Evidence Collection & Submission Manual – CFS Evidence Submission Guidelines - Forensic Biology/DNA

Evidence Collection & Submission Manual – CFS Evidence Submission Guidelines – Forensic Biology/DNA

Forensic Biology/DNA

Daniel Cowen, Senior DNA Scientist

The Forensic Biology/DNA section receives biological evidence as part of a homicide, sexual assault, burglary, and other types of criminal investigations. The section identifies bodily fluids and performs DNA analysis on items of probative value to the case. The section performs DNA analysis using both nuclear autosomal short tandem repeats (STRs) and Y-STRs. Current DNA technologies can be used to include or eliminate individuals as having contributed genetic material associated with evidence from a crime scene. In addition, the DNA laboratory serves as a local casework database site for the entry and searching of DNA profiles in the State of New York and the National Combined DNA Index System (CODIS). This database can be used to link unsolved crimes to each other, identify a previously convicted offender as a contributor of the crime scene DNA, or to associate unidentified remains with missing persons.

Submission Guidelines

Evidence that may yield a probative DNA profile for cases without an arrest should be submitted to the CFS if needed for investigative purposes as determined by a law enforcement agency or if needed for prosecution purposes as determined by a prosecutor’s office. Evidence that may yield a probative DNA profile for cases with an arrest should be submitted at the request of the attorney’s office. If probative information is obtained from the analysis of an item, the testing of additional items may be deferred.

In major cases it is valuable to have a meeting with CFS staff, detectives, attorneys, and crime scene personnel to prioritize evidence and to discuss the case in its entirety to ensure the best and most efficient analysis occurs. Prior to homicide evidence being submitted for analysis (with the exception of firearms evidence), it will be required for a meeting between the submitting agency, attorney’s office (if applicable), and CFS staff of all relevant sections to occur. Exceptions will be made for exigent circumstances with approval of the CFS.

Possible weapons, suspect’s clothing (if the victim may have bled or for wearer’s DNA if the clothing was left at the scene by the perpetrator), victim’s clothing (if the perpetrator may have bled), or other items that may link the perpetrator to the crime scene should be submitted for analysis. Known DNA standards from the victim may be requested prior to commencement of DNA analysis.

Initially, a sexual assault kit and/or used condoms should be submitted. Victim’s clothing may be submitted at a later date if the sexual assault kit is negative for probative evidence. Bedding and other items should only be submitted if other evidence do not yield probative information and after approval from the CFS.

Items belonging to the suspect and left at the scene by the perpetrator such as blood; saliva from bottles, cans, cigarette butts, and chewing gum; tools such as screwdrivers, and flashlights; or clothing items such as hats, shirts, glasses, and gloves should be submitted. For cases with arrested suspects, the CFS may contact the submitting agency and attorney to see if analysis is necessary and may request submission of the known DNA standard from the suspect prior to analysis. For crime scene samples that may have been handled or used by the victim, the CFS may request submission of the known DNA standard from the victim prior to analysis.

All firearms submitted to the laboratory will be swabbed for DNA analysis, and a report will be issued unless the examination is formally waived by the District Attorney’s Office. Any additional DNA analysis will be detailed in a subsequent report.

Trace evidence is defined as evidence that has no visible staining and would contain DNA that only results from touching an item with the skin. Trace evidence will only be analyzed if profiles are not generated from other probative evidence. If probative information is obtained from one item, testing of additional items may be deferred. For non-violent crimes, a maximum of two trace items will be analyzed per case unless exceptional circumstances have been discussed with the CFS.

Items that will not be analyzed for trace DNA:

Ammunition and fired cartridge cases (with the exception of shot gun shells and cartridge cases from homicides).

Fired cartridge components may only be submitted for DNA analysis if there are visible body fluids present.

Items that will not be analyzed for trace DNA for non-violent crimes:

Trace evidence swabs of counters, walls, light switches, doors etc. from public locations. Touch items or swabs of items that were generally handled by the victim and believed to only have been touched briefly by a suspect such as padlocks, tools, jewelry boxes, doorknobs, light switches, electrical cords, etc.

Requests for items identified as not subject to trace DNA analysis will be canceled by the laboratory. If you believe analysis is warranted, please contact the section supervisor for further consideration

Proper Handling / Minimizing Contamination

Use only clean gloves and utensils
Change gloves often and in-between handling different items
Do not talk, sneeze, or cough near evidence
Do not process items for latent prints with same brush or by dipping into container of powder

Proper Collection – General

Always package evidence for biological analysis in PAPER. Never use plastic bags or containers (with the exception of sharps; see How to Submit Evidence Page).
If items are being collected at the scene for touch DNA, two swabs should be collected per item.
Be sure to document what/where the swab was collected from.
Package items separately to avoid cross-contamination.
Wet items should be dried prior to packaging and stored in breathable containers.
Store in a dry, room temperature environment to preserve DNA.
Any liquid body fluids should be stored in a refrigerator prior to submission.
Any human tissue or bones should be stored frozen prior to submission.

Proper Collection of Stains

For large items or hard to handle items with obvious stain patterns, collect stained item directly by cutting out a smaller area.
Do not perform field-test directly on a stained area.
Collect liquid or wet stain directly onto sterile cotton swabs.
Collect dry stains using sterile swabs lightly moistened with water (do not dilute stain).
Substrate control swabs are NOT needed.