Intro to Forensic Science and Crime Labs

Intro to Forensic Science
Crime Laboratories
What is Forensic Science?
• Forensic Science is the study and application
of science to matters of the law.
• The term CRIMINILISTICS can be used
synonymously with FORENSIC SCIENCE
– Interchangeable (same meaning)
3 Major Avenues Available to Police
Investigators in Solving a Crime
• Confessions
• Some suspects may be coerced into confessions for fear of longer
sentences even though they are innocent
• Eyewitness Accounts by Victims or Witnesses
• Eyewitness accounts vary considerably from person to person
• Eyewitness accounts are unreliable and have led to the
imprisonment of many wrongfully convicted suspects
» INNOCENCE PROJECT – Project with aim to free wrongfully convicted
• 87% of all wrongful convictions were a result of flawed
eyewitness testimony
• Evaluation of Physical Evidence Retrieved From the Crime
• Only physical evidence is free of inherent error or bias
• Relies on science
Functions of a Forensic Scientist
• Find, examine, and evaluate evidence at a crime scene
• Observational skills are key!
• Must observe whole crime scene
– Avoid tunnel vision
– Collect all evidence and don’t jump to
• Use analytical skills to examine evidence and draw conclusions
– ANALYTICAL SKILLS = the ability to identify a problem, isolate its
component parts, organize information for decision making, and
evaluate information to draw conclusions
– Using DEDUCTIVE REASONING- using logic while studying all known
facts to come to a conclusion
• Act as expert witnesses for prosecution or defense attorneys
Crime Labs
• Nearly Four hundred public crime labs in US
– More than 3 times that of 1966
• Growth due to…
– Supreme court cases in 1960’s placed more
emphasis on police securing scientifically
evaluated evidence
– Increased Crime Rates
– Increased Drug Abuse- All evidence from illicit
seizures must be sent to crime Lab for chemical
Crime Lab Challenges
• Not enough labs to keep up with needs
• DNA Profiling (Fingerprinting)- Major Reason for increased
– Technology did not exist prior to early 1990’s
– Traces of Blood, Saliva, Hair, Epithelial Tissue (Skin), and Semen
backlog crime labs
– Over 57,000 unanalyzed case samples
– Untested convicted offender samples over 500,000
– Tested samples go to CODIS (National DNA Databank)
• Combined DNA Index System
– Some states have own Database
– CA over 1 million in state database
» 3rd Largest in world
» Starting in 2008 all people arrested and suspected of felony charges were profiled
Types of Crime Laboratories
• Federal Crime Laboratories
– FBI Crime Lab (Quanitico Virginia), largest in WORLD
– DEA, and Bureau of Alcohol, Tobacco, Firearms, and
Explosives located within
– Will offer assistance and expertise to state and local
• State and Local Crime Laboratories
– State Labs, Most States Have State Lab
• Some have statewide system with regional satellite labs
– County and Municipal Crime Labs
• Some Counties have
• Larger Cities, NY city is largest.
• Many smaller cities do not have due to cost
Specialty Units With Full Service
Crime Laboratories
• Biology Unit (Staffed w/ Biologists and Biochemists)
DNA Profiling
Blood Evidence and Other Bodily Fluids
Hair and Fiber Analysis
Plant Materials Such as wood and Plants
• Firearms Unit
– Ballistics (Bullet and Firearm Analysis)
– Gun Powder Residue
– Crime Scene Reconstruction (Distance from which weapons are
• Document Examination Unit
– Handwriting and Typewriter Analysis
– Ink and Paper Analysis
– Erasures/Depressions
Specialty Units With Full Service
Crime Laboratories (continued)
• Photography Unit
– Examines and records physical evidence through
– Sometimes advance techniques used (infrared, X-Ray,
digital imaging ect…)
• Toxicology and Drug Analysis Unit
Examines Body Fluids and Organs
Detect Presence or absence of drugs and poisons
Evidence may be sent to separate 3rd party facility
Often maintain field instruments such as Intoxilyzer
• Fingerprint/Latent Fingerprint Unit
– Fingerprint Analysis
Specialty Units With Full Service
Crime Laboratories (continued)
• Polygraph Unit
– Lie Detector
– Investigator tool yet not forensic scientist tool
– Still kept in crime lab unit though
• Voiceprint Analysis Unit
– Use sound spectrograph that transforms speech in to visual display
called voiceprint
– Analyze recorded voice evidence (Tape recorder/phone calls ect…)
• Crime Scene Investigation Unit
– Collect and preserve physical evidence that is later analyzed at crime
– Must maintain chain of custody and check evidence in to evidence
Other Forensic Science Services
• Forensic Psychiatry
– Used in criminal and civil proceedings
• Determine competence
• Evaluate behavioral disorders
• Forensic Odontology
– Id victims in unrecognizable state
– Bite mark analysis
• Forensic Engineering
– Failure analysis (buildings)
– Accident reconstruction
• Examine, photograph, and review of mechanical objects
• Forensic Computer and Digital Analysis
– Newest and fastest growing
– Identification, collection, preservation, and examination from
computers and other digital devices

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