Biology/DNA Detail Casework Unit
The casework unit is responsible for processing evidence from homicides, sexual assaults, robberies, burglaries, auto thefts, weapons violation cases, and many other crime types.
The Casework Unit can analyze a variety of sources for DNA to include blood, saliva, seminal fluid, and skin cells. DNA is found on a variety of evidence items to include weapons, smoked cigarettes, used condoms, fingernails, bottles, cans, cups, ligatures, and glasses (to name a few).
Several basic steps are performed during DNA testing regardless of the type of sample being tested. The general procedure includes:
- DNA is removed from the cells through the addition of chemicals
- Millions of copies of the DNA is made through an amplification process called Polymer Chain Reaction (PCR)
- DNA is analyzed using a capillary electrophoresis genetic analyzer
- DNA results are compared and interpreted from the unknown and known samples to determine whether the known individual is excluded or included as being the source of the DNA
- If there is a DNA match, statistics are performed to determine the strength of any such match
Any probative biological sample that has been stored dry or frozen, regardless of age, may be considered for DNA analysis.
DNA profiles obtained from items of evidence believed to be from the suspect may be entered into the Forensic Index of the Combined DNA Index System (CODIS).
CODIS, is operated, supported and managed by the Federal Bureau of Investigation. The purpose of CODIS is to aid investigations by providing leads. Names, social security numbers, ID numbers and other personally identifiable information are not stored in CODIS. The database is simply comprised of DNA profiles and special codes to identify which forensic laboratory entered the genetic information. DNA profiles obtained from forensic cases that are eligible for CODIS entry are automatically entered into the database by the Biology/DNA Detail of the LVMPD. Genetic profiles contained in CODIS are searched against each other on a weekly basis, and any matches that occur are called hits. CODIS hits can link forensic cases to other forensic cases and/or link convicted felony offenders or arrestees to forensic cases. All pertinent CODIS hit information is disseminated to the investigating agent(s) by the Biology/DNA Detail.
Sample Limitations Policy
In order to ensure analysis of the most probative evidence, to meet casework demands, and to provide for the responsible use of resources, the Forensic Laboratory has implemented sample limitations in the Biology/DNA Detail. For details regarding the sample limitation policy, please refer to the following table:
| Crime Category
||Maximum # of Evidence Items Accepted
|| Maximum # Reference Samples Accepted
| Homicide (see NOTE below)
| Sexual Assault (see NOTE below)
(including a sex assault kit)
| Crimes Against a Person
(Robbery, Kidnap, Assault, Attempted Felonies)
| Weapons Violations
(MDPP, Larceny, Explosive Devices, Recovered Property, Arson)
| Property Crimes (Burglary, Auto Theft)
Analysis on “touch” DNA evidence will not be performed on property crimes
NOTE: Although limits have been established, exceptions to policy will be made when analysis is required on additional items associated with homicides and sexual assaults and some touch DNA property crime cases (i.e., cases associated with a series). The Laboratory, in coordination with the investigators, will evaluate these situations on a case by case basis.