Chapter 2: Crime-Scene Investigation & Evidence CollectionMiss Colabelli

Principle of Exchange

The first part of Locard’s Exchange Principle Whenever two people come into contact with each other, a physical

transfer occurs Ex: hair, skin, cells, clothing fibers, pollen, glass fragments, debris, makeup

Transferred materials are considered to be trace evidence Pet hair, hair on a brush, fingerprints on glass, soil tracks from shoes,

drop of blood on clothing, paint chip

The second part of Locard’s Exchange Principle The intensity, duration, and nature of the materials in contact determine

the extent of the transfer Ex: More transfer would occur between two in a fist fight as opposed to

two people brushing past another

What is Evidence?

Information that can and should influence the beliefs of an observer (judge and jury) about a specific legal question

Ex: guilty or innocent, liable or not

Evidence must be relevant to the question at hand

Relevant Evidence Having the ability to make existence of any fact that is important to the case

more probable or less probable (FRE401)

Probative Evidence Having the ability to prove or demonstrate something relevant to the case

Prejudicial Evidence Not allowed in court, mislead jury, wasting time, unnecessary

Types of Evidence

Direct Evidence Firsthand observations that include an eyewitness account,

police video cameras, or confessions Ex: an eyewitness states they saw the defendant pointing a gun at

the victim. The testimony in court by this witness would be direct evidence.

Types of Evidence

Circumstantial evidence Indirect evidence that can be used to imply a fact but not

directly prove it Ex: finding a suspect’s gun at the site of a shooting is evidence

that the suspect was at the scene of the crime Can be physical or biological in nature Most physical evidence reduces number of suspects to a

smaller group of individuals Physical ex: fingerprint impressions, footprints, shoe prints, tire

impressions, tool marks, bullets/shells, weapons, fibers Biological evidence can reduce the number of suspects to a

very small amount even down to one, more persuasive in court Biological ex: body fluids, hair, plant parts, natural fibers

Types of Evidence

Class Evidence Narrows down an identity to a group of

persons or things Ex: the blood type of a sample from a

crime scene tells us that a person with that same blood type may have been there

Individual evidence Narrows an identity to a single person or

thing Typically has a unique combination of

characteristics that can only belong to one person

Ex: fingerprints

Crime Scene Investigation Team

Legal and scientific professionals who work together to solve a crime

Police officers Usually first to arrive at the crime

scene District attorney may be present to

determine whether a search warrant is necessary for investigators

Crime-scene investigators Document the crime scene in detail

and collect physical evidence Record data, sketch artists,

photographers, evidence collectors

Medical examiners (coroners) Determine the cause of death

when homicide has occurred

Detectives Look for leads by interviewing

witnesses and talking to the crime-scene investigators about evidence

Specialists Vary depending on the case ex:

entomologists, forensic psychologists

The Seven S’s of Crime Scene Investigation

Securing the Scene Responsibility of the first-responding police officer Safety of all individuals is first priority Preservation of evidence is second priority

Protects area within the crime scene, restrict all unauthorized persons from entering

Keep security log of all those who visit the crime scene Collect pertinent information and request additional needs

required for investigation May request more officers or various teams of experts to come

to scene

The Seven S’s of Crime Scene Investigation

Separating the witnesses Witnesses must not be allowed to talk to each other

To avoid witnesses working together to create a story (collusion) Their eyewitness accounts will be compared after interviewing The following questions need to be asked

When did the crime occur? Who called in the crime? Who is the victim? Can the perpetrator be identified? What did you see happen? Where were you when you observed the crime scene?

The Seven S’s of Crime Scene InvestigationScanning the scene

Determine where photos should be taken Determination of primary crime scene and secondary crime

scene and assigning priorities regarding examination Ex: a murder may have taken place in one location (primary scene)

and the corpse found at another location (secondary scene)

The Seven S’s of Crime Scene InvestigationSeeing the scene

Photos of the overall area and close-up photos with and without a measuring ruler should be taken

Triangulation of stationary objects should be included in photos as reference points

Full view of the crime scene should be taken from several angles, views, and distances

Several close-up photos of any evidence and bodies should be taken

The Seven S’s of Crime Scene Investigation

Sketching the scene Accurate rough sketch of the crime scene is made

Noting position of body and/or other evidence All objects are measured from two immovable landmarks

including other objects in the vicinity (doors, windows, furniture)

If scene is outdoors, position of trees, vehicles, hedges… will be noted

North should be labeled and scale of distance provided After rough sketch, a more accurate copy will be made to use

in court Computer programs are available to recreate these sketches more

accurately

The Seven S’s of Crime Scene Investigation

Searching for evidence Depending on the amount of investigators, a spiral, grid,

linear, or quadrant pattern should be walked Location of evidence marked, photographed, and sketched Additional light sources might be needed to find hair and

fibers Flashlights and forceps for collection of evidence is preferred

to avoid picking up unnecessary materials

The Seven S’s of Crime Scene Investigation

Securing and collecting evidence All evidence needs to be properly packaged, sealed, and

labeled Procedures and techniques for evidence collection and storage

must be followed Liquids and arson remains are stored in airtight, unbreakable

containers Biological evidence is usually stored in breathable containers

so evidence can dry out, reducing the chance of mold or contamination

After the evidence has dried out, it is packaged in a paper bindle then placed in a plastic or paper container that is sealed with tape and labeled with the signature of the collector written across the tape

Packaging Evidence

Evidence log and chain of custody document must be attached to evidence container Case number Item inventory number Description of evidence Name of suspect Name of victim Date and time of recovery Signature of person recovering the

evidence Signature of any witnesses present during

collectionhttp://school.cengage.com/forensicscience/home.html

Packaging Evidence

Procedure are as follows1. Choose the appropriate-size sheet of clean paper for the

bindle2. Crease the paper as shown in figure3. Place the evidence in the middle location4. Fold left and right sides in5. Fold in top and bottom6. Insert the top flap into the bottom flap then tape closed7. Place bindle inside plastic or paper evidence bag. Fold the

bag closed8. Place a seal over the folded edge of the evidence bag9. Have the collector write his/her name over the folded edge

https://www.youtube.com/watch?v=98167mF32jw

Chain of Custody

Individual who finds evidence marks it for identification and bags the evidence in a sealed plastic or paper container where it is labeled with pertinent information

Container is then given to next person to bring to the lab and sign over to a technician

After analysis, evidence is resealed in original packaging and resealed then sign the chain of custody log to ensure evidence is responsibly handled

Analyze the Evidence

Processes the evidence collected to determine facts about the case Technicians are only specialized in one type of evidence

Laboratory results are sent to lead detective which usually leads to a crime-scene reconstruction Forming a hypothesis of the sequence of events from before

the crime was committed and walking through its process

Analysis can Link a suspect with a scene or a victim Establish identity of a victim or suspect Confirm verbal witness testimony Even acquit the innocent

Crime-Scene Reconstruction

Forming a hypothesis of the sequence of events from before the crime committed through its commission

Lead detective determines how evidence fits into the crime scene while being compared to witness accounts

Some evidence might be staged and it’s important that investigators examine all possibilities

Staged Crime Scenes

When evidence does not match the testimony of witnessesArson

Perpetrator stages a fire to cover other crime such as murder or burglary

Suicide/murder Victim is murdered, and perpetrator stages scene to look like a

suicide by causing death by alcohol or overdose

Burglary To collect insurance money

Staged Crime Scenes

Initially treat all deaths a homicideDo the types of wounds match the weapon employed?Could wounds be self-inflicted?Establish profile of victim through interviews of family/friendsEvaluate behavior of victim before eventEvaluate behavior of any suspects before eventCorroborate statements with evidential factsReconstruct the eventConduct all forensic examinations to determine facts about

case

Case Study: Lillian Oetting (1960)

Three Chicago socialites were murdered in Starved Rock State Park, Illinois. All three woman had fractured skulls. Their bodies, bound with twine, were found in a cave. Near the bodies of the women, a bloodied tree limb was found and considered to be the murder weapon. Because all three women had been staying at a nearby lodge, the staff from there were questioned. Chester Weger, a 21 year old dishwasher at the lodge, was asked about a blood stain on his coat. He said it was animal blood. He agreed to take a lie detector test and passed it. He was requestioned and took a second lie detector test and passed again. The blood on his coat was examined and it indeed was animal blood. The case reached a dead end.

Investigators decided to revisit evidence. The rope used to bind the women was examined more carefully. The twine was a 20-stranded twine only sold at Starved Rock State Park. Identical twine was found in an area accessible to Weger. He again was the prime suspect. The blood was re-examined from his coat by the FBI and was found to be human and compatible with the blood from one of the victims. Weger took a third lie detector test and failed. He was found guilty for the murder of one woman, Lilliam Oetting and spent over 45 years in prison. He recently petitioned the Governor of Illinois for clemency, saying he was beaten and tortured into making a confession. He still claims he is innocent.

Case Study: The Atlanta Child Murders (1979-1981)

Wayne Williams is thought to be one of the worst serial killers of adolescents in the U.S. history. His victims were killed and thrown into the Chattahoochee River in Georgia. Williams was questioned, because he was seen near where a body had washed ashore. Two kinds of fiber were found on the victims. The first kind was an unusual yellow-green nylon fiber used in floor carpeting. Through the efforts of the FBI and DuPont Chemical Company, the carpet manufacturer was identified. The carpet had been sold in only 10 states, one of them being Alabama, where Williams lived. Thus, the fibers found on the victims were linked to carpet fibers found in Williams’ home.

Another victim’s body yielded the second type of fiber. This fiber was determined to be from carpeting found in pre-1973 Chevrolets. It was determined that only 680 vehicles registered in Alabama had a matching carpet. The probability of both types of fibers being owned by the same person were about 29 million to one. Williams was convicted and sentenced to two life terms.