The body of a 15-year-old girl was found naked and bound in the woods near the side of an interstate in December 1996, about three months after she was reported missing.

A man who had a campsite near where the body was found in Maryland was interviewed by detectives for three years, without an arrest. But Lloyd Arbard Harris, now 53, was arrested two decades later for the rape and murder of Stacy Lynn Hoffmaster, according to the local newspaper of record, The Frederick News-Post.

The approaching October trial will include evidence Harris did not want included: a traditional test for indicating the presence of semen, according to the latest court decision.

Acid phosphatase is an enzyme found in many bodily fluids—but in especially great amounts in semen.

Prosecutors contend its presence on Hoffmaster’s body indicates she was raped—and also that there was enough of it to determine the sexual assault occurred shortly before she was killed, according to the newspaper reporting.

Harris and his public defender had attempted to bar some of the testimony of Stephen Cina, the former Cook County, Illinois, medical examiner and witness for the prosecution.

The defense attorney argued that the body was exposed to the elements, and the presence of microbes and other contamination on the test swabs meant the state could not prove when the semen was deposited on the remains. But the presiding Frederick County Circuit judge ruled on June 30 to allow the testimony.

A series of studies dating back to the 1970s and 1980s appear to indicate that acid phosphatase’s breakdown is gradual, and predictive of the time of deposition.

Harris’ attorneys have previously made other arguments that were dismissed by the judge: that prosecutors took too long to indict the suspect; that the district attorney did not specify Hoffmaster’s time of death; and that the campsite Harris frequented near the location of the body should have expectations of privacy, and require a search warrant. The judge ruled against those arguments, and several others.

Hoffmaster’s decomposed remains were discovered Dec. 23, 1996, underneath a blanket near Interstate 70 and East South Street. Harris was interviewed in 1996, 1997 and 1998—and finally in 2016, at the time of his arrest. A new lead investigator was assigned the case in 2014, and police reportedly re-interviewed witnesses and retired detectives, leading to the 2016 arrest of Harris.

The suspected murderer faces life in prison without parole on the first-degree charges, if convicted.