Biology/DNA
Forensic Scientists in the Biology section conduct examinations to locate and identify blood, semen, saliva, and other body fluids and biological materials on items of physical evidence. DNA testing is then performed to determine possible sources of the body fluids and biological materials identified. To do this, the DNA types obtained from the evidence samples are compared to the DNA types obtained from the known reference samples (victim, suspect or elimination) samples to determine if the DNA types are the same. DNA profiles from evidence samples are also entered into the state and national DNA databases for comparison to offender DNA profiles and DNA profiles from other evidence samples.
Local, county and state law enforcment officers have the opportunity to submit biological evidence to the SD State Forensic Lab for DNA testing. DNA results obtained by the SD State Forensic Lab are used by law enforcement for investigative information and by SD Judicial Systems to assist in the resolution of criminal matters. DNA databasing of South Dakota's offender samples is being accommplished according to SDCL 23-5A-1 and the FBI's CODIS/NDIS protocols.
Current Chemistry
We are currently quantifying samples using the Quantifiler Trio quantification kit which determines the amount of DNA present in the sample, if degradation is present, and if any inhibitors are present that could adversely affect downstream processing. The Globalfiler amplification kit is used to amplify evidence samples, which includes 21 autosomal markers, amelogenin (sex determining) marker and two male specific markers. Compared to the previous amplification kit, the GF kit has added the two male specific markers and increased the number of autosomal markers from 15 to 21.
The biology section also utilizes the Y-Filer Plus amplification kit. This kit amplifies DNA only on the Y-chromosome and is specific to males. This chemistry is mainly used for complex sexual assault cases. The use of this kit allows us to detect a small amount of male DNA present in samples with a very large amount of female DNA that the GF kit may not detect.
Validations
- Veriti Thermocyclers
- Automate express robots
- A second 3500 Genetic Analyzer
- A second QIAgility liquid handler
Equipment
The ABI 3500 Genetic Analyzer which is an eight capillary machine that can hold up to two plates of 96 samples. It takes ~ 36 minutes to run one row of eight samples. This machine replaced the ABI 310 Genetic Analyzer which had one capillary and would take ~36 minutes to run one sample. In conjunction with the GeneMapper ID-X software, the ABI 3500 Genetic Analyzer determines the DNA types that are present in a sample.
The QIAgility liquid handler can hold up to 96 samples and is used to prepare sample plates for the quantitation and amplification steps. These steps were previously done by hand and this machine has saved up to two days of examiner time.
The Copan CPA200 Puncher is a machine used to punch samples from FTA cards (database sample collection cards) directly into a plate for testing. This replaces hand punching which is very time consuming and decreases contamination risks or loss of sample from static.
