Criminal Investigatio

ns

Investigators should approach the crime scene investigation as if it will be their only opportunity to preserve and recover… physical clues. They

should consider other case information or statements from witnesses or

suspects carefully in their objective assessment of the scene.

Investigations may change course a number of times during such an

inquiry and physical clues, initially though irrelevant, may become crucial to a successful resolution of the case.

What is the goal of a criminal investigation? The goal of criminal investigations is NOT to

catch criminals.

Investigators must collect evidence that can be used in court to convict them.

If investigators don’t follow proper procedures, they open themselves up to courtroom attack by defense attorneys.

In some cases, if police do not follow proper procedures, the court will not even allow the evidence to be introduced.

The Crime Scene *Preliminary Investigation is done by patrol officers.

Securing the Scene Interview victims Interview witnesses

*The detectives document the scene.

Take official statements

Note Conditions Photograph and

videotape the scene

EVIDENCE Detectives must carefully

mark all evidence taken from the scene.

They place the items in special plastic envelopes, seal it, and write the date and time.

Anyone who looks at the evidence afterward, must also mark the date and time, to establish a chain of custody to assure that the evidence was not tampered with.

Line- Ups, Show- Ups and Throw Downs

If people witness a crime, detectives will try to get them to identify the suspect.

Although eye-witnesses are sometimes unreliable, they are still used to “solve” a crime.

Lineups Show-Ups Throw Downs

Lineups Show-Ups Throw Downs

5 or 6 people, one of which is the suspect

stand on a stage so

witnesses can view them

The witness is shown a

single suspect

Detectives show pictures

fro the witness to

choose from

Which method do you think is

the most reliable and

why?

Informants What is an informant?

People who give intelligence about what is going on in the criminal community.

Most are low level criminals involved in so called “victimless crimes”

Informants can provide information that an officer could get only by going undercover and working for months to gain the trust of criminals.

Criticism of the use of Informants!

Most informants are criminals Questionable reliability Do not make good witnesses at trial

because juries tend not to believe them.

Informants themselves do not want to testify, because they don’t want to be branded as a “snitch”

Do you agree with the use of

Informants during a criminal

investigation?

Criminal Investigation:

Is this the One? With your Do Now Partner, read each of the cases on the worksheet and answer the attached questions.

We will discuss our answers!