Improved genetic testing was credited for the indictment last week of an imprisoned rapist on charges in another attack, which occurred more than a decade ago.
An Anne Arundel County grand jury indicted 44-year-old William Robert Dempsey on Friday in connection with a Sept. 10, 1989, sexual assault of a woman in an abandoned building in Laurel.
Dempsey, formerly of Odenton, is serving a 25-year sentence for another 1989 rape.
More-sensitive genetic testing enabled county police - whose lab routinely retests DNA from unsolved crimes - to build a case they could not make at the time of the incident, said State's Attorney Frank R. Weathersbee.
"The test back in '89 was so primitive that we weren't able to come up with anything," he said.
Since then, advancements in DNA testing have enabled authorities to obtain numerous "hits" through genetic data banks that resulted in solving old and new cases.
The most serious of the seven counts on which Dempsey was indicted is rape, which carries a maximum penalty of life imprisonment.
According to charging documents, the woman met a man she knew as "Bill," and he asked her to take him to Laurel.
The man eventually took her into an abandoned building off Route 198, where she was bound and raped while the man held what the woman believed to be a straight-edge razor to her throat.
The woman subsequently freed herself and ran to a highway, where motorists stopped to help her, the documents say.
Police identified Dempsey as a suspect then, but the laboratory reported that it "could not positively state the DNA matched," according to the charging documents.
The rape case was among several reopened last fall for new genetic testing, the documents say.
Dempsey was charged in 1989 with the other rape, and he pleaded guilty in 1990, according to Anne Arundel Circuit Court records.
He is imprisoned in Hagerstown for assault, robbery and burglary, state Department of Corrections officials said.