The Forensic Biology section of the Forensic Science Laboratory performs serological and DNA analyses of physiological fluids and other biological materials from the human body for identification and comparison purposes. The type of material typically examined includes, but is not limited to: blood, semen, saliva, urine, skin cells and hair collected at crime scenes and from articles of physical evidence.  These types of biological material are frequently deposited or exchanged during the commission of violent crimes such as homicides, rapes, assaults, burglaries, and hit and run fatalities.  The Lab’s analysis of biological crime scene evidence may link that material to victims and/or suspects, thus aiding criminal investigations.

The Forensic Biology section analyzes approximately 800 cases per year submitted from over 50 different law enforcement agencies throughout Westchester County.  Personnel from this section perform laboratory analyses on samples submitted by police agencies and the County District Attorney’s Office.  They also assist in the processing of crime scenes.  Fifteen full time analysts, as well as other support personnel, are currently employed in this section.

Examination of biological evidenceBiological Evidence
Upon submission, articles of biological evidence are stored in a secure refrigerated walk-in cold room pending analysis.  An analyst is assigned to a specific case and will bring the evidence to an evidence examination room, where it is documented and analyzed. The alternate light source (ALS) can be utilized to locate stains that may contain blood, semen, saliva or urine. These stains will undergo a series of presumptive screening tests. Any stains testing positive during this stage may then be subjected to more extensive testing, including DNA analysis. The DNA profiles generated from these stains can then be compared to samples taken from known sources (victims, suspects, etc.).  

Some biological material containing DNA may not be suitable for presumptive screening, such as skin cells and hair.  These types of material are collected and preserved in the laboratory for possible future DNA analysis.

Automated DNA analysisAnalysis
The Forensic Biology section performs DNA STR (Short Tandem Repeat) analysis.  STRs offer the advantages of short analysis time, a high degree of discrimination, and the ability to look at small and degraded samples of DNA.  For example, the tissue adhering to the end of a pulled head hair or skin cells from under the nails of a victim can be compared to possible contributors.

This laboratory currently utilizes high-throughput Applied Biosystems 3130 multicapillary Genetic Analyzers for DNA analysis.  In addition to the analysis of autosomal STR’s, the laboratory performs STR analysis of the Y chromosome, found only in males.  Analysis of Y STR’s is helpful in the investigation of sexual assault cases involving multiple male assailants and in highly degraded samples.

The Forensic Biology section is linked to the FBI CODIS (Combined Dna Index System) DNA database network comprised of local, state and national databases. Through this network the Laboratory is able to take an unknown crime scene DNA profile and compare it to other unsolved cases throughout the country.  The same crime scene sample will also be compared against convicted offender databases.  These CODIS links allow investigators from different jurisdictions working on serial-type cases to share important investigative information at an early stage.   CODIS also maintains a dedicated database for unidentified human remains.

Crime Scene Analysis
In addition to providing analytical testing utilizing state-of-the-art DNA technologies, the Forensic Biology section provides field services to law enforcement agencies investigating crime scenes.  Upon request by a police agency, the forensic laboratory will provide assistance in the detection and collection of biological and trace evidence at a crime scene. The laboratory can dispatch personnel trained in the use of the alternate light source and chemical enhancement techniques for the detection of blood and other body fluids as well as impression evidence such as from footwear.  Additionally, the laboratory employs specially trained personnel that can examine bloodstain patterns and provide investigative information on how these patterns may have been generated.