Franklin County Chief Probation Officer Richard A. Mertz estimated about two dozen adults and a dozen juveniles in the county have given DNA samples since December 1996.
If someone is on probation, Mertz said his department has the blood sample drawn at Chambersburg Hospital. If the offender goes to jail, the county prison has inmates tested before their release.
If police find blood, semen or other DNA evidence at a crime scene, it can be checked against state and national databases, Mertz said.
He said the database is limited to sexual offenders in Pennsylvania, but many states test all convicted felons. He predicted it will expand to other crime categories in the state.
"We just received notice this week from Tennessee that if we transfer any felon there for courtesy supervision they must agree to DNA testing when they arrive," Mertz said.
DNA Lab Manager Christine Tomsey said the lab has almost 9,000 blood samples from convicted felons. Genetic profiles have been done on about 800, but she said the pace will pick up at the new lab.
At the lab, blood samples are transferred to a special paper that can be frozen and stored. A section of the paper the size of a postage stamp is cut out for genetic profiling.
The profile is digitalized and put into state and national computer databases, Tomsey said. To assure confidentiality, a sample is assigned a number when it arrives and a different number when it is put in the databases.
Only she and the Combined DNA Indexing System administrator at the lab have the key to link a number to a name, Tomsey said.
While the profiles are unique to individuals, Tomsey said there are no physical or biological characteristics in the profiles, such as their sex or race.
The lab also keeps "unidentified question samples" from unsolved crimes. Tomsey said those can be compared to offenders' profiles as they are entered into the system.
Tomsey said the laboratory has done DNA profiling since about 1990, although the database for convicted sex offenders is less than two years old.
"There have been about 200 hits across the country," she said of crimes being linked to people in the national DNA system. So far she said no one in the state database has been linked to another crime.