Criminal Investigations 1.The Crime Scene 2.ID Suspect 3.Informants

Criminal Investigations  The goal of criminal investigations is not simply to catch criminals.  Investigators must also collect evidence that can be used in court to convict them Innocent until proven guilty  Two of the most common investigatory techniques are searches and interrogation

The Crime Scene 1.Secure the Crime Scene -Usually handled by the Patrol Officer -Pursue and arrest suspect -Call detectives if needed 2.Document the Crime Scene -Take statements from witnesses -Note conditions at the time of crime -Take pictures and identify objects 3.Build Case File -All documentation taken at the crime scene -Physical evidence taken to evidence room 4.Chain of Custody is established -Each new person who takes custody of the case must also write the date and time and sign it. -Each custodian may be called during a trial

ID Suspects  If people witness a crime, detectives will try to get them to identify the suspect.  Three methods of for witness to identify suspects: Line up Show up Throw down *These methods can be suggestive

Bell Ringer11/12/13  What was the policing strategy that was placed in New York? Briefly explain, did it work?  What was the policing strategy that was placed in San Diego? Briefly explain, did it work?  What happen in Houston?

Informants  Many police officers develop a network of informants, who give intelligence about what is going on in the criminal community  Most informants are low level criminals  Police commonly use informants to get search warrants  Informants usually ask for something in return Cash

Informant Reliability  Most informants are criminals Reliable Say what they are told Trying to get out of trouble  Jail-house informants SC has ruled that police cannot deliberately elicit incriminating statements from indicted defendants without an attorney If cellmates without prior police contact offer information to police, it can be used in court. * Police defend the use of informants as a necessary evil

Crime Labs  More than 300 accredited crime labs exist  The FBI operates the nations largest, which examines evidence from other federal, state, and local agencies as well as from FBI cases.  The FBI divides the crime lab into units each specializing in one area: Trace Evidence Unit Questioned Documents Unit The Firearms and Toolmarks Unit The Latent Print Unit DNA Analysis Unit

Trace Evidence Unit  Examines: hairs, fibers, ropes, cordage, feathers, plants, woods, soils, glass, and building materials  Find traces of material and compare against what they have on file  Can match fibers to clothing as well as color, length and style of hair

Questioned Documents Unit  Studies anything that has to do with paper. From determining what a piece of paper is made of to analyzing handwriting and breaking codes. Deals with machines that use paper. Also handles footprints and tire tracks Maintains collections of anonymous letters, bank robbery notes, fraudulent checks, office equipment, shoe prints and tire tracks.

Firearms and Toolmarks Unit  Investigates guns, ammunition, evidence with residue from gunshots, tools, motor vehicles numbers and serial numbers.  Maintains a collection or firearms, ammunition and their distinctive markings  Ballistics experts can tell what kind of a gun fired a bullet.

Latent Print Unit  Analyzes fingerprints  Everyone has fingerprints, and they remain the same throughout life.  Since 1924, the FBI has had a fingerprint unit.  Now also look for fingerprints, palm prints, foot prints and even lip prints  They use lasers, alternative light sources, chemicals as well as powders.  The FBI’s Automated Fingerprint Identification System is used by all to match prints

The DNA Analysis Unit  The genetic code that determines a person’s physical characteristics.  Each human cell holds the complete genetic blueprint for each individual  DNA is compared from suspect to DNA found at the crime scene

Bell Ringer 11/13  What are the Miranda Rights?  What does it mean to be in custody?