The DNA Unit is divided into two specialized sub-units: the Nuclear DNA Sub-Unit and the DNA Database Sub-Unit. DNA, or deoxyribonucleic acid, is the genetic material that makes each person unique. It is found in the nuclei of cells and can be extracted from body fluids or skin cells.
Nuclear DNA Sub-Unit
The Nuclear DNA Sub-Unit focuses on analyzing DNA extracted from various biological sources, such as body fluids, bones, hair roots, and skin cells. The Nuclear DNA Sub-Unit analyzes DNA from the cell nucleus using STR (short tandem repeats) analysis. Short Tandem Repeat (STR) analysis, a highly effective and widely used forensic technique that is automated for efficiency. STR analysis is used for generating DNA profiles from crime scene evidence, which are then compared to other profiles or reference samples to aid in investigations.
DNA profiles produced in this sub-unit are entered into the Combined DNA Index System (CODIS). CODIS allows for matches between evidence profiles and profiles from convicted offenders, as well as cross-referencing evidence from different cases, such as missing persons or unidentified human remains. These comparisons provide direct investigative leads to law enforcement.
The DNA Unit reports two main types of database hits:
- Offender Hits: When a DNA profile from crime scene evidence matches the profile of a convicted offender in CODIS.
- Forensic Hits: Matches between evidence from different cases, helping to identify links between incidents, missing persons, or unidentified remains.
DNA Database Sub-Unit
The DNA Database Sub-Unit is responsible for processing DNA samples from convicted offenders and uploading their profiles into CODIS. This system operates at three levels:
- State Level (SDIS): Matches crime scene profiles with offenders within the state of Connecticut.
- National Level (NDIS): Expands the search to include offenders across the United States.
Profiles from both forensic evidence and convicted offenders in Connecticut are uploaded to the National CODIS Database, enabling cross-state searches and expanding the reach of investigations.
CODIS also plays a critical role in identifying missing persons and remains, broadening its impact on forensic investigations nationwide.
Database DNA Sub-Unit
The Database DNA Sub-Unit processes DNA from convicted offenders and uploads their profiles into CODIS. CODIS operates on three levels:
- Local Level (LDIS): For city or county labs.
- State Level (SDIS): Matches crime scene profiles with offenders within the state.
- National Level (NDIS): Matches crime scene profiles with offenders across the country.
Forensic Biology and Hair Analysis
The Forensic Biology Unit examines hair to determine if it is human or animal. For human hair, they check if it was forcibly removed, naturally shed, or treated. If the hair cannot be tested for nuclear DNA, it is sent to the Mitochondrial DNA Sub-Unit for further analysis.
Improvements in Workflow
In 2013, the DNA Unit created a separate lab area for processing "known" samples. These samples include blood or buccal swabs from identified individuals. The separate lab helps speed up processing. It also prevents contamination with evidence samples. Better communication with agencies has led to more elimination samples. This helps refine comparisons and avoid unnecessary CODIS entries.