In January 1994, the Crime Lab began accepting cases in its statewide Deoxyribonucleic Acid (DNA) testing program. The DPS labs that currently provide DNA testing include Austin, Garland, Houston, Waco, McAllen, Corpus Christi, El Paso, and Lubbock. The DPS statewide DNA program provides this service free of charge to those agencies not supported by city and/or county crime laboratories in Dallas, Fort Worth, San Antonio, Austin, or Houston.
DNA is the building block for all life and is unique for each individual. This technique enables the lab to more accurately identify or eliminate a suspect in a criminal case. Under proper conditions, DNA analysis can produce positive identification comparisons to known blood and tissue samples. DNA analyses identify the genotype of an individual at up to 15 locations on their DNA chain, as well as indicating whether they are male (XY) or female(XX). DNA may be obtained on items submitted to the Crime Laboratory Service from crime scenes, including blood stains, whole blood, seminal fluid, tissue, saliva, and, sometimes, hair samples. Known reference samples are needed for identification comparisons. A DNA analysis of the evidence samples from sexual assault or homicide victims will be performed, and this DNA compared with DNA profiles from a suspect, or with DNA profiles in the CODIS offender database, to ascertain whether a previously convicted offender has committed the offense. The uniqueness of DNA profiles typically allows the scientist to report the probabilities of a suspect matching evidence in a crime to one in several billion.
The number of cases on which DNA analysis is employed is increasing annually at a rapid rate.