When crimes are joined at trial

Law and Human Behavior, Vol. 9, No. 2, 1985

When Crimes Are Joined at Trial*

E d i t h G r e e n e t a n d E l i z a b e t h F . L o f t u s t

In two experiments, subject-jurors read evidence from actual criminal cases, decided on the guilt of the defendant, and answered several additional questions. The defendant was accused of one charge (murder or rape) or two charges (both murder and rape). In both experiments, the defendant was more likely to be convicted of either crime if the two charges were joined in one trial. Trait ratings indicated that the defendant was perceived in a more negative way when standing trial on two offenses. The order in which the charges were heard had no effect, nor did instructions to subjects to judge the cases separately.

I N T R O D U C T I O N

Rule 8 of the Federal Rules of Criminal Procedure allows criminal offenses to be joined for trial if they are of a similar character or if they arise in the same incident. This rule has been adopted in most state jurisdictions. The rationale for permitting crimes to be tried together is the savings of time and money for the judicial system. This rule may carry with it substantial costs to the administration of justice, however, because of the possible disparity in outcomes between joint and single trials. In fact, Horowitz, Borden, and Feldman (1980) and Tanford and Penrod (1982) have data showing that jurors' ratings of a defendant's guilt are higher when crimes are joined than when the offenses are tried separately.

We propose three hypotheses to account for the anticipated changes in conviction rates between single and joined trials. (From here on, we refer to this as the spillover effect, because evidence of multiple offenses seems to spill over onto, and distort, evidence presented on any single charge.) First, people who learn that a defendant is charged with multiple crimes may infer more negative characteristics about that person than would people who know the suspect is on

* Portions of this paper were presented at the American Psychology-Law Society Meeting in Cam- bridge, Massachusetts, October, 1981. The research was supported by a grant from NSF to Elizabeth Loftus.

t Department of Psychology, University of Washington, Seattle, Washington 98195.

193

014%7307/85/0600-0193504.50/0 �9 1985 Plenum Publishing Corporation

194 GREENE AND LOFTUS

trial for only one wrongdoing. As Rosenberg and Sedlak (1972) have pointed out, people will infer from knowledge of one negative trait that a person possesses other negative traits as well. This "halo" effect may cause jurors who read evidence of multiple crimes to infer that if the defendant is being charged with several offenses, he or she must possess some sort of "criminal disposition."

A second hypothesis involves the standard of proof that jurors use in deciding to convict. The "reasonable doubt criterion" used for convicting a suspect charged with two crimes may be lower than the criterion used to convict a suspect charged with only one. This idea can be explained in terms of differing threshold probabilities for different situations. For example, Nagel, Lamm, and Neef (1978) noted that women are relatively less concerned about convicting an innocent defendant in rape cases than in robbery cases. The rape case may be emotionally upsetting to them and this emotional response may affect their decision making. Analogously, if jurors are distressed that a defendant may have committed several offenses rather than just one, they may lower the criterion needed for conviction.

A third hypothesis has to do with memory for evidence presented in these cases. There are at least three ways that jurors' memory could be affected. People who hear evidence of multiple charges may have more difficulty remembering all of the details of the cases compared to subjects who get evidence of only one crime. This is the "memory load" hypothesis. Also, when crimes are joined, evidence relevant to one charge may be remembered as being connected with the second or third offense. This is the notion of "semantic integration" whereby information from different sources is integrated in memory (see, e.g., Bower, Black, & Turner, 1979). Tanford and Penrod found that the higher probability of conviction in a joined trial was caused in part by jurors confusing facts between the combined offenses. Finally, if jurors can store only a certain number of details in memory, particularly when given evidence from several cases, they may remember only the most salient information, often information that confirms their verdict (Greene, 1981). This is the "differential memory" hypothesis.

In Experiment 1, people read evidence of one or two offenses, and were asked questions pertaining to their sentiments about the defendant, memory of the evidence, standard of reasonable doubt, and likelihood of guilt. We compared the results from one case presentation to those that followed when the charges were combined.

E X P E R I M E N T 1

Methods

Subjects

Subjects were 90 undergraduates at the University of Washington who par- ticipated in groups of 5 to 15.

Materials

Case Descriptions. Two criminal case descriptions were taken from San Jose

WHEN CRIMES ARE JOINED AT TRIAL 195

Police Department Offense Reports. Joinder of charges is a genuine issue here, because a pretrial motion to separate these offenses was offered and denied. One report described evidence collected by police investigating a homicide and the second described evidence concerning a rape. One suspect had allegedly committed both crimes. For this study, the police reports were edited so that only the most important evidence was used, and the names of all parties were changed. Also, because police reports rarely contain exculpatory information, we included an alibi witness to ensure that there would be no ceiling effect for convictions. The murder scenario was approximately 900 words long; the rape scenario approximately 780 words long.

The case descriptions were pretested to be certain that there was no ceiling effect when the crime was presented in isolation. 45% of the subjects who read the murder scenario thought the suspect was guilty, while 60% of those who read of the rape chose the guilty verdict.

Dependent Measures

First, as a test of the ~ disposition" hypothesis, subjects were asked to rate the defendant on these three dimensions: dangerousness, likeableness, and believability. They used a 7-point scale where 1 = Definitely not dangerous, and 7 = Definitely dangerous. Secondly, as a test of the "memory load" hypothesis, they answered a 20-item recognition test that dealt with details presented in either the murder case or the rape, depending on which they had read. (Subjects who were presented with both offenses gave their ~atings of the defendant, then answered the questions relevant to the first charge before they com~ pleted the questionnaire items that dealt with the second charge.)

Five of the 20 questions tested the "differential memory" hypothesis. Sub- jects who read multiple charges may be more likely to misremember evidence in the direction of guilt, so we included a distractor in each of these five questions that would test this possibility. For example, in the description of the murder, this information was given: "Mary Arca, an employee of the 7-11 stove adjacent to the victim's apartment, remembered that at approximately 2:30 AM on the morning of the murder, she was picking up some trash in the parking lot and observed a man walking down the stairs of the victim's apartment. She was fairly certain that the man was Craig LeRoy Gerdes, the defendant." On their recognition test, subjects were asked this question: "When Mary Arca reported her version of events to the police, how certain was she that the man seen walking down the steps of the victim's apartment was the defendant Gerdes?" (a) Very certain; (b) Fairly certain; (c) Uncertain; (d) No information was given. We reasoned that people who had known about the multiple charges and thought the defendant was guilty might remember that the witness was very certain of her identification. Subjects who read about the single charge might err in either direction. The remaining 15 items tested memory of other details in the descriptions.

The next dependent measure had to do with the notion of reasonable doubt. It presented the judge's instruction on reasonable doubt/presumption of innocence and then asked: If all of the evidence available in this case adds to 100%,


what is the minimum percentage of evidence that you would require to find the defendant guilty of criminal homicide (forcible rape) beyond a reasonable doubt?" Finally, subjects were asked to estimate how guilty they thought the defendant was, using a 7-point scale where 1 = Definitely not guilty, 2 = Probably not guilty, 3 = Possibly not guilty, 4 = Uncertain etc. to 7 = Definitely guilty.

Procedure

The experiment involved a 24-hr retention interval. On the first day of the study, subjects read the case descriptions, were told that they would later be tested on some of the material, and were asked to return at the same time on the following day. One-third of the subjects (N = 30) read the description of evidence on the murder, one-third read about the rape, and one-third read of both the murder and rape, always in that order. On the second day of the study, subjects returned to answer the questionnaire.

Results

Guiltiness Ratings

A major result is the comparison between verdicts on the murder and rape charges when those crimes are presented alone, relative to when the charges are given together. The mean guiltiness rating for the murder when presented alone was 4.07 (on a scale from 1 to 7) and for the murder when presented in combination with the rape, 5.33, F(1,58) = 18.66, MSe = 1.29 (p < .01). The mean rating for the rape when presented alone was 4.63 and when presented in combination, 5.33. This difference was nonsignificant, F(1,58) = 2.23, MSe = 1.06, p > .10. At least in one instance, however, guiltiness ratings show evidence of the spillover effect: subjects are more likely to believe the defendant is guilty of murder when they know that he is also being charged with rape than if they think he is on trial for one offense only.

These data can also be interpreted as if the conviction variable was dichot- omous. Here, the proportion of subjects who thought that the defendant was possibly, probably, or definitely guilty when they read evidence of only one crime is compared to the proportion who thought he was guilty when they knew he was being charged twice. The proportion of people who found the defendant guilty of murder jumps considerably when a second charge is added (.43 vs..83). Similar data came from the rape charge (.60 vs. .80). Analogously, the proportion of subjects who found him not guilty dropped substantially when the charges were combined (.33 vs. .10 for murder; and .17 vs. .03 for rape).

Mechanisms by Which Spillover Effect Occurs

As a test of the "criminal disposition" hypothesis, subjects gave ratings on the dimensions of dangerousness, likeableness, and believability, and their mean responses are given in Table 1.

WHEN CRIMES ARE JOINED AT TRIAL !97

Tab le 1. M e a n D a n g e r o u s n e s s , L ikeab leness , a n d Bel ievabi l i ty R a t i n g s for 3 Case P r e s e n t a t i o n s a

Experiment 1

Case presentation

Murder Rape Murder & Rape

Dangerousness 4.10 4.10 5.57 Likeableness 3.90 2.73 2.73 Believability 3.63 3.37 2.53

a 1 = low and 7 = high.

When two charges were presented, the defendant was indeed judged to be more dangerous, F(2,87) = 7.65, MSe = 2.51; less likable, F(2,87) = 17.46, MSe = 1.38; and less believable, F(2,87) = 11.36, MSe = 1.74 than when only one crime was described (all p 's < .05). On the dimension of believability, that result held for both the murder alone and in combination, t = 3.32, p < .01; as well as for the rape alone and in combination, t = 2.40, p < .05.

A second hypothesis to explain the spillover effect was the changing standard of reasonable doubt. Subjects were asked to give the minimum amount of evidence that they would need to find the defendant guilty beyond a reasonable doubt, given that all the evidence in the case adds to 100%. The mean standard used by subjects who read of the murder alone was 83.30%. When the murder was presented with the rape, the mean on murder was 86.30%. The rape standards were 73.70% when presented alone and 83.70% when given together with the murder charge. None of these differences are significant (all F 's <1).

The third hypothesis was that subjects are remembering the evidence differently in these three conditions. In terms of overall number of recognition items answered correctly, there were no significant differences between groups; mean number of correct responses on the murder questionnaire was 10.73 (out of 20 items) when given alone, and 9.97 when presented in combination. Mean number correct on the rape questionnaire was 13.10 when given alone and 13.00 when given with the murder. Nor was there a significant effect for the five items that included a distractor subjects might select if they thought the defendant was guilty. In general, subjects were not more likely to recognize information consistent with their verdicts, although the trend is in that direction. When subjects who read the murder scenario thought that the defendant was guilty, they incor- rectly chose the "guilty alternative" answer on 1.31 of the five questions. When they thought he was not guilty, they chose that response on .88 of the five questions. In sum, we did not find support for either the "memory load" or ~ ential memory" hypotheses. Subjects were equally accurate in their responses to test items, whether they read one case description or two.

Discussion

The most important result of this experiment is that a defendant is more


likely to be convicted by mock jurors of any one charge when that offense is combined with another at trial. What causes the spillover effect? One difference between jurors who have two cases to decide and jurors with only one is that the former group rate the defendant as being less believable, less likable, and more dangerous. The differences in guiltiness ratings may result from the inference jurors make about the defendant's character. Thus, jurors in the first group may be more likely to convict the defendant because a criminal disposition "predis- poses" one to break the law, or because the act of convicting an "unworthy person" is less oppressive than convicting a "worthy person." On the other hand, because the causality involved in trait ratings is unclear, it is conceivable that verdicts may cause the character inferences. A person who is found guilty may be thought of as a more negative person than one who is acquitted. The exact mechanisms at work here cannot be specified without more precise questioning of subjects, but it seems clear that jurors' sentiments toward the defendant are different when they know he is charged with multiple crimes.

E X P E R I M E N T 2

The purpose of Experiment 2 was twofold. First, because some appeals courts assume that a judicial instruction will caution jurors to consider the evidence on each charge separately and other courts have stated that an instruction is not sufficient to eliminate prejudice, we tested the effectiveness of one such cautionary instruction. Secondly, we wanted to further specify the spillover effect by determining when, during the trial, it was likely to occur.

The first issue concerns the effectiveness of the multiple offenses instruction. In U . S . v . Foutz (1976), the court stated "We cannot presume that the jury adhered to limiting instructions and properly segregated the evidence into separate intellectual boxes." The court reversed the convictions of a defendant found guilty of two robberies that occurred several months apart. In U .S .v . Adams (1970), however, the appeallate court thought that a limiting instruction was effective and upheld the convictions of a defendant found guilty of both the sale and possession of heroin, offenses that were separated by several months.

Is a cautionary instruction able to undue the prejudice that occurs when offenses are joined? In Experiment 2, some jurors were given the multiple offenses instruction that is currently used in Washington State, other jurors were not. Also, we varied the time at which the instruction was given to determine whether it would be more effective if presented before the evidence was heard. Kassin and Wrightsman (1979) found that when judges' instructions preceded a trial, jurors were less likely to think the defendant was guilty, in comparison to when the instructions came at the end of trial. They reasoned that jurors may evaluate the evidence differently if they are instructed before hearing any testimony, and that by the end of trial, the instructions may be ineffective if jurors have already made a decision. By analogy, an instruction before trial may caution jurors to not let evidence on one charge influence their verdict on any other.

The second issue concerns the timing of the spillover effect. Does the prej-

WHEN CRIMES ARE JOINED AT TRIAL t99

udice accrue as a juror is hearing, processing, and storing evidence of multip|e offenses? Or is it apparent only when a juror is forced to render a verdict, or do both of these possibilities contribute to the spillover?

We addressed these questions by varying the order in which the offenses are presented. Our procedure and rationale are as follows: some subjects judge only one charge (first degree murder -M-, or first degree rape -R-); a second group of mock jurors read evidence of the murder followed by the rape charge against the same defendant (Group MR); and a third group read of these same two crimes in reverse order (Group RM; see Figure 1). For the latter two groups, jurors read evidence of the first charge and are forced to hold that information in memory until evidence of the second charge is presented. Only when the entire trial has been completed do they give their verdicts on the two charges.

Suppose the spillover effect occurs after evidence on both charges has been presented and while the verdicts are being reached. In that case, the order in which the offenses were presented should not matter since spillover distorts only guilt determination and not the processing of evidence. Therefore, guiltiness ratings for the murder in Group MR should be about the same as the ratings for murder in Group RM, and the ratings on rape in Group RM should compare to the ratings in Group MR.

On the other hand, if the spillover distorts processing of the evidence, it might affect only the crime presented second in order. Jurors' decisions on the first charge would not be affected by what they later learn about a second charge, but their decision on the second charge would be affected by evidence from the first. So for example, guiltiness ratings for the murder in Group RM should be higher than ratings on murder in Group MR. In fact, this hypothesis predicts that the conviction ratings on murder would be about the same for MR and for M.

Finally, if the spillover effect distorts both the processing of information and choice of a verdict, then the guiltiness ratings for the murder will be highest for Group RM (spiUover effect both at processing and when a verdict is chosen), intermediate for Group MR (spillover effect only when a verdict is reached), and lowest for Group M.

Method

Subjects

Subjects were 166 undergraduates at the University of Washington who par- ticipated in groups of 4 to 8.

Materials

Trial Transcripts. The case descriptions used in Experiment t were rewritten in the form of excerpts from a hypothetical trial. Subjects read opening statements by both attorneys, testimony of prosecution and defense witnesses, and the at- torney's closing arguments. Finally, brief instructions were given that explained burden of proof, reasonable doubt, and elements of the crime. These instructions were taken from the Washington State Pattern Instructions--Criminal (1977). The


trial transcripts presented the same witnesses and described essentially the same evidence that was presented in the scenarios. There were two transcripts: one described the murder charge; a second described the rape.

Questionnaire. The questionnaire used in Experiment 2 was similar, but not identical, to the one used previously. Subjects first rated the defendant on scales of dangerousness, likableness, and believability. Next, they estimated how guilty the defendant was on a 7-point scale. A question pertaining to reasonable doubt was reworded: "The defendant should be found guilty if there is at least a __% change that he committed the crime." In this experiment, subjects who thought the defendant was possibly, probably, or definitely not guilty had the opportunity to "convict" the defendant of a lesser included offense. We reasoned that jurors who judge two offenses and decide the defendent is not guilty of the crimes in question might still be more likely than jurors with just one case to convict the defendant on a less serious charge, if given that option. The question on lesser included offenses was worded: " I f you are not satisfied beyond a reasonable doubt that the defendant is guilty of first degree murder, the defendant may be found guilty of a lesser crime, if the evidence is sufficient to establish the defendant's guilt of such a lesser crime beyond a reasonable doubt. The crime of first degree murder includes the lesser crimes of second degree murder and manslaughter. (At this point, definitions of those lesser crimes were given.) Do you think the defendant is guilty of second degree murder?". Subjects answered on a 7-point scale. Finally, jurors who said "Not guilty" to this question were asked "Do you think the defendant is guilty of manslaughter?" There was a comparable set of lesser-included options on the rape charge. The 20 multiple choice recognition questions for each charge were nearly identical to the recognition questions used in Experiment 1. A few of the questions were reworded in an attempt to see whether subjects remember evidence that is consistent with their verdicts.

Design and Procedure

Subjects were randomly assigned to all conditions. Ninety-six subjects read evidence of two offenses. They read through both transcripts before anwering questions about either. One third of the subjects (n = 32) read the multiple offense instruction before the trial transcripts, one-third read it after the transcripts, and one-third were given no instruction. The multiple offenses instruction was taken from the Washington State Pattern Instructions--Criminal (1977) and read this way: "A separate crime is charged in each count. You must decide each count separately as if it were a separate trial. Your verdict on one count should not control your verdict on any other count." This instruction variable was factorially combined with a second variable, the order of the multiple offenses, to yield six groups of subjects who read about two crimes. One-haft of the subjects in each instruction condition (n = 16) read the murder charge first; the other half read the rape charge first (see Figure 1). Of the people who were given evidence of only one charge, 36 read about the murder and 34 read about the rape. They read the same trial transcripts and answered the same questions as subjects in the multiple offense condition. Only the multiple offenses instruction was missing.


Severed Cases

M R

Murder Rape

(Murder) (Rape)

Joined Cases

Order Murder-Rape

MR, Before (Murder & Rape)

MR-After (Murder & Rape)

MR-None (Murder & Rape)

Order Rape-Murder

RM-Before (Rape & Murder)

RI~-After (Rape & Murder)

~-None (Rape & Murder)

Instructions Before

Instructions After

No Instructions

Fig. 1. Design of experiment 2, verdicts to be reached are shown in parentheses.

Results

Single vs. Joined Trails

Guiltiness Ratings. The mean guilt estimate for the murder in combination with the rape was 4.36; for the murder alone, 3.50, F(1,130) = 11.00, MSe = 1.78, p < .001. The mean rating for the rape when combined with the murder was 4.22 and when given alone, 3.62, F(1,130) = 4.05, MSe = 2.29, p = .046. This result parallels the finding of Experiment 1: subject jurors are more likely to convict a criminal defendant of any one charge when they read evidence of multiple offenses as compared to when only one crime is being tried.

Another way to describe the rating results is as though they were dichoto- mous judgments (guilty-not guilty). Subjects who thought that the defendant was definitely, probably, or possibly guilty are combined into one group and compared to subjects who thought the defendant was not guilty. Subjects who were uncertain are not included in this analysis. The percentage of guilty verdicts is higher in a joint trail than in a single trial (for murder: 46%, joined, vs. 19%, single; for rape: 44% vs. 29%). Also, the percentage of not guilty verdicts drops for a case tried in combination with a second (for murder: 29%, joined, vs. 47%, single; for rape: 35% vs. 59%). These data clearly demonstrate the spillover effect.

One possible outcome of this experiment is that jurors confronted with multiple charges would convict on one or the other charge, but not both. We found no evidence of this. If jurors decided that the defendant was guilty of murder, they were more likely to convict him of rape. The mean guilt estimate on the rape charge was 4.52 from subjects who voted for conviction on murder, and 3.46 fi'om subjects who opted for acquittal on murder. Similarly, the mean guilt estimate on the murder charge was 4.78 from subjects who voted for conviction on rape, and 4.03 from subjects who acquitted on rape.

Mechanisms by Which Spillover Effect Occurs. The mean dangerousness rating for the joined trial (MR and RM) was 4.23; for the murder trial alone, 2.58; for the rape trial alone, 2.79, F(2,163) = 25.62, MSe = 1.90, p < .001. T- tests confirmed that the ratings for both single cases were significantly lower than

202 G R E E N E AND LOFTUS

T a b l e 2. M e a n d a n g e r o u s n e s s a n d be l i evab i l i t y r a t i n g s as f u n c t i o n o f v e r d i c t a

Exper iment 2

Dangerousness Believability Murder charge

Verdict

Guilty 4.801 b 3.001 c Not guilty 2.87 J 3.96 J

Rape charge Verdict

Guilty 4.75 ] o 2.73 ] c Not guilty 3.06- 3.96 ~

a 1 = low and 7 = high. b p less than .001. c p less than .005.

the rating from the joined trial. Subjects who read about two charges rated the defendant as less believable than did people who read of either the murder or the rape alone. The mean believability rating for the joined trial was 3.20; for murder, 4.19; for rape, 3.71, F(2,163) = 9.42, MSe = 1.45, p < .001. Here, t-tests showed that ratings from single trials were both significantly higher than the believability rating from a joined trial�9 There were no differences in subjects' ratings of how much they liked the defendant, regardless of whether they read one or two charges, F(2,163) = .42, MSe = 1.58, p > .20.

Not surprisingly, subjects who found the defendant guilty rated him as more dangerous (p < .001 for both murder and rape convictions) and less believable (p < .005 for both cases) than subjects who thought he was not guilty�9 These results are shown in Table 2.

All subjects were asked "The defendant should be found guilty is there is at least a __% chance he commited the crime." The mean percentage for the murder when presented with the rape was 83.95%; when presented alone the percentage was 88.10%. For the rape charge, the mean percentage when combined with the murder was 86.45%, when given alone, 86.50%. These figures are in the predicted direction, but are not significantly different (all F 's < 1). Nor were there significant differences in answers to this question dependent upon whether student-jurors had decided that the defendant was guilty or not guilty of either charge�9

We thought that subjects who read evidence from two crimes might be more likely to convict on a lesser-included offense than subjects who read of only one charge. For example, if these people acquitted the defendant of first degree murder, they might be more likely to convict him of second degree murder or manslaughter�9 On a scale from 1 to 7 where 1 = Definitely guilty and 7 = Definitely not guilty, the mean guiltiness ratings on the charge of a second degree murder were 3.75 (joined) and 3.37 (single) F (1,75) = 2.78, MSe = 1.29, p > �9 10. The ratings on the manslaughter charge were 3.31 (joined) and 2.75 (single), F (1,61) = 2.88, MSe = 1.76, p > .05. These differences were nonsignificant, as were the differences in ratings relevant to rape.


Our prediction about memory performance is quite straightforward: because jurors who read testimony on two charges have twice the amount of information to hold in memory, they should make more errors on a multiple choice recognition test than people who judge only one offense. Mean number correct of 20 questions about the murder case was 14.44 (joined) and 15.03 (single); about the rape case, 15.04 (joined) and 15.44 (single). While differences were in the predicted direction, none of them reached significance. Furthermore, none of the five critical questions showed the effect that we had anticipated: that an incorrect multiple choice alternative would be chosen significantly more often by subjects who read of two crimes than by those who read of only one.

One "memory" effect did emerge, however. Specific errors on the recognition test depended upon whether a juror decided that the defendant was guilty. For example, the rape victim testified that she listened to a series of voiceprints in an attempt to recognize the voice of her assailant and that she was moderately certain she had selected the right man. One of the multiple choice questions asked: "How certain was the victim of her voiceprint ID?" (a) Absolutely certain; (b) Quite certain; (c) Moderately certain; (d) Uncertain. Whether subjects read one case or two did not affect their answers to this question; the factor that influenced their responses was their verdict. That question was answered correctly by 44% of the people who voted for conviction and 65% of the people who opted for acquittal. More interestingly, the two multiple choice answers that were in the direction of guilt [alternatives (a) and (b)] were chosen by 54% of the subjects who convicted the defendant, but by only 31% of the subjects who acquitted him. Subjects who opted toward conviction remembered that the victim was more certain of her identification than she actually had been, Chi square = 4.85, 1 df, p < .05.

What about subjects who voted for acqui t ta l - -were they more likely to choose an answer in the direction of innocence than subjects who convicted the defendant? Apparently not: alternative (d) was the response we thought subjects might select if they thought the defendant was innocent. But only 4% of those who voted for acquittal chose this answer, and 2% of subjects who thought the defendant was guilty selected alternative (d).

Effect of Instructions

One purpose of this experiment was to assess what effect, if any, an instruction on the use of evidence from multiple charges would have on guiltiness ratings. This variable has no relevance to subjects who read about only one charge so their data are not included in this analysis. We predicted that an instruction given before the presentation of evidence might be more effective in reducing prejudice than an instruction given at the end of the trial. The mean guiltiness rating on the murder for the group given instructions before the trial was 4.31; for the group who read the instruction at the end of triM, 4.16; and for the group given no instruction, 4.63, F(2,90) = 1.10, MSe = 1.66, p > .20. Analogous data came from the rape trial. The mean guiltiness ratings were 4.13 when instructions were before trial; 4.34 when instructions were after; and 4.19 with no instructions, F(2,90) = .18, MSe = .41, p > .20.


The presence of the instruction in this simulation seems not to affect jurors' verdicts. In fact, subjects who heard the multiple offenses instruction were only slightly less harsh in their verdicts than jurors who had no instruction. The presence of an instruction also had no effect on jurors' impressions of the defendant, their standards of reasonable doubt, or their memory of information given in the trial transcripts. In one instance, the presence of an instruction resulted in a significantly lower guiltiness rating on a lesser included offense, third degree rape, than when no instruction was given. This analysis encompasses jurors who re- fused to convict the defendant of either first or second degree rape. The mean guiltiness rating on the third degree rape charge was 2.78 when the instruction came at the beginning of trial; 2.50 when it came at the end; and 4.14 when it was absent, F(2,20) = 3.68, MSe = 5.67, p = .04.

Order of Multiple Offenses

Another purpose of this study was to determine what effect the ordering of multiple offenses would have on mock jurors' decisions about the guilt of a criminal defendant. When the murder charge was presented before the rape, subjects' mean guilt estimate on the murder was 4.31; and when the charges were given in reverse order, the rating on the murder was 4.42, F(1,90) = .16, MSe = 1.66, p > .20. The mean guiltiness rating for the rape was 4.15 when that charge was presented first, and 4.29 when the rape was presented second, F(I,90) = .22, MSe = 2.28, p > .20. For neither charge were there significant differences in guilt estimates that followed from different orderings of these crimes, although the ratings were somewhat lower for each charge when it was given first.

We suggested that if the spillover effect occurs during processing of the trial information, there would be a higher guiltiness rating for a crime judged second in a series, relative to the same crime judged first or alone. This is so because a juror's processing of the evidence on that second charge would be distorted by evidence previously given on the first crime. Results from this experiment failed to support such a hypothesis. We also suggested that if the spillover effect occurs only when a verdict is reached, it should make no difference in which order the charges are presented; guiltiness ratings should be equivalent whether that crime was described first or second. Our data seem more consistent with this second hypothesis.

Overall, the order in which the crimes were given had no significant effect on jurors' responses to any questions asked of them. Their impressions of the defendant did not change depending upon the ordering of charges, nor did their standards of reasonable doubt, responses to the lesser included option, or memory of the evidence.

G E N E R A L D I S C U S S I O N

In both experiments, subject-jurors delivered harsher verdicts on a criminal


charge when that crime was combined with another at trial, than when that case was presented alone. Furthermore, both experiments support the hypothesis that the spillover effect may be caused at least in part by the inference people make about the defendant's criminal disposition. However, given the design of our experiments, we cannot rule out another interpretation. It is possible that the arrival of a guilt verdict led subjects to reevaluate the defendant's character and to find him less believable, less likable, and more dangerous than if they had acquitted him. Sorting out the direction of this causality will be a direction for further research.

Another factor that could partially explain the spillover effect involved differences in subjects' memory of the evidence. Athought we found no differential memory between groups of subjects, there may have been differences in the accuracy of jurors' memories which we were unable to detect. Tanford and Penrod asked their subjects to list as many items of evidence as they could remember that were against the defendant, and then to do the same with evidence in the defendant's favor. They found that the joining of charges led to a higher intrusion of facts from other offenses. It is quite possible that had we asked subjects to recall items of evidence rather than recognize them, we would have shown some differences in subjects' memories depending on the number of transcripts they read. One other factor may have contributed to the absence of memorial differences. In Experiment 2, subjects answered their questionnaires immediately after they had read the trial transcripts. In an actual trial, a longer retention interval would certainly intervene. Perhaps this longer retention interval would result in more errors by people who had twice the amount of information to keep in memory.

One result of this research complements a finding by Tanford and Penrod in showing that when subject-jurors made errors in their recollection of the evidence, those errors are sometimes biased toward conviction. In Experiment 2, we found that subjects who thought the defendant was guilty were more likely to choose a multiple choice alternative that pointed towards conviction than an alternative that was neutral or supportive of acquittal. This selective memory effect did not occur when subjects thought the defendant was not guilty (i.e., they were not more likely to choose the alternative that supported acquittal). Tanford and Penrod's data show that when charges were joined, there were more intrusions of facts that were against the defendant than in his favor. They interpreted these intrusions as indicative of a bias towards guilt.

Some courts have assumed that any bias against a defendant tried for multiple offenses would be mitigated by instructions to the jury to consider the evidence on each charge separately. Our data showed that no matter when it was presented, the instruction was ineffective in reducing guilt estimates to the level obtained from subjects who judged only one offense. Tanford and Penrod have data that showed essentially the same result, but one difference in our procedures is worth mentioning. In their study, the instructions were given as part of the general introductory instructions to the experiment. In our study, subject-jurors heard the actual multiple offense instruction that is used in criminal trials in Washington


State, and when that instruction was given at the end of trial, it was included as part of the judge's usual charge to the jury. Even with this closer approximation to courtroom practice, the multiple offenses instruction was ineffective.

We varied the order in which two offenses were presented in an attempt to see when, during the trial, the spillover phenomenon occurred. We reasoned that if the spillover effect occurs at the time that a juror must decide on verdicts, the guiltiness ratings on a charge presented first should approximate the ratings for that same offense described secondly. In turn, they should be higher than the rate for the same crime given alone. Our data seem to support this hypothesis, although there may be other explanations for this finding. First, it is possible that jurors may not reach a verdict only when requested to do so, but instead may decide in the midst of the trial. Given this possibility, it is difficult to pinpoint the spillover effect to the verdict determination stage only. Secondly, we cannot rule out the possibility that spillover could still be occurring during processing of the trial evidence. We predicted that if this was true, evidence relevant to the second offense would be influenced by information on the first charge. On the other hand, earlier evidence may be viewed differently in light of more recent evidence. These offsetting influences may explain the equivalence in guilt estimates whether an offense is presented first or secondly at trial. What this reaseach can do is rule out one explanation--that the spillover effect occurs ONLY because earlier evidence colors jurors' interpretation of more recent information.

Tanford and Penrod also varied the order in which the multiple offenses were presented. They ended with mixed results. They found, as we did, no effect of order on conviction ratings, but these data resulted from varying the order of four cases when the particular charge in question was criminal trespass. They did find an order effect when they varied the order of three cases, however. Here, subjects assigned higher guilt ratings when a rape charge came last than when it came first. It is difficult to specify why they found an order effect in one instance and not in another. Possibly, the use of different charges influence these results.

In a slightly different test of the effect of order of multiple charges, Davis, Tindale, Nagao, Hinsz, & Robertson (1983) presented a short videotaped trial in which the defendant was charged with three offenses. Davis et al. varied the order in which the charges were deliberated, not the order in which they were presented, so their findings relate only tangentially to our study and the Tanford- Penrod work. Nonetheless, they found interesting effects of order: the more serious a preceding charge, the higher the conviction rate of mock jurors. In ad- dition, they found that a guilty verdict on a preceding charge increased the likelihood of conviction. More relevant to our work is their contention that the order effect could possibly be caused by subjects attributing a criminal disposition to the defendant. At least this explanation could not be disconfirmed, and there was no evidence of recall failure or testimony confusion as the basis of the effect.

The experiments reported here have shown that a defendant is judged more harshly if he or she is on trial for multiple offenses than if only one crime is being tried. While these findings seem reliable, the usual caveat about the external validity of simulation studies must be made. Given that these were mock jurors


who completed a questionnaire while fully aware that their verdicts were not binding, it is premature to assume that real jurors impaneled in a courtroom would behave in an identical way. Our methodology somewhat limits the generalizability of results in other ways as well. For example, the relative absence of memory effects may have been due to the limited amount of evidence that substituted for a trial. Similarly, the absence of an effect of the cautionary instruction may have resulted because jurors did not deliberate. Other research has shown that when jurors have the opportunity to deliberate, they sometimes discuss and try to clarify the judge's instructions, and that such discussion tends to strengthen the impact of the instructions on their decision making (Severance, Greene, & Loftus, 1984). Perhaps the most significant point to be made about these studies is that preliminary investigation of the potential for prejudice has begun. As future research starts to dismantle some of the artificialities inherent in the present situ- ation, we will be in a better position to truly assess the costs that we must pay for the sake of expedience in the criminal justice system.

R E F E R E N C E S

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Bray, R. M., & Kerr, N. H. Use of the simulation method in the study of jury behavior: Some methodological considerations. Land and Human Behavior, 1979, 3, 107-119.

Davis, J. H., Tindale, R. S., Nagao, D. H., Hinsz, V. B., & Robertson, B. (1983). Order effects in verdicts from consideration of muttiple offenses. Cited in Davis, J. H. Order in the courtroom. In Muller, D. J., Blackman, D. G., & Chapman, A. J. (Eds.) Perspective in Psychology and Law, in press.

Drew v. U.S. 331 Federal Reporter, 2nd series. 85 (D.C. Circuit, 1964). Greene, E. Whodunit? Memory for evidence in text. American Journal of Psychology, 1981, 94,

479-496. Horowitz, I. A., Bordens, K. S., & Feldman, M. S. A comparison of verdicts obtained in severed

and joined criminal trials. Journal of Applied Social Psychology, 1980, 10, 444-456. Kassin, S. M., & Wrightsman, L. S. On the requirements of proof: The timing of judicial instructions

and mock juror verdicts. Journal ofPersonali~ and Social Psychology, 1979, 37, 1877-1887. Nagel, S., Lamm, D., & Neff, M. Decision theory and juror decision-making. Paper presented at

International Society for Political Psychology, New York, 1978. Rosenberg, S., & Sedlak, A. Structural representations of implicit personality theory. In L. Berkowitz

(Ed.), Advances in Experimental Social Psychology, Vol. 6, New York: Academic Press, 1972. San Jose Police Department Offense Reports, Nos. 81-2224, 79-1368063. Severance, L. J., Greene, E., & Loftus, E. E Toward criminal jury instructions that people can

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of Applied Social Psychology, 1982, 12, 453-480. U .S .v . Adams. 443 Federal Reporter, 2nd series, 756 (2nd circuit, 1970). U .S .v . Foutz. 540 Federal Reporter, 2nd series, 733 (4th circuit, 1976). Washington Pattern Instructions--Criminal. St. Paul: West Publishing Co., 1977.

When crimes are joined at trial

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