A pair of socks has helped police in the US solve the killing of a Pennsylvania woman - almost 30 years after it happened.

Theodore Dill Donahue has been charged with the murder of his then-girlfriend Denise Sharon Kulb in 1991, according to state authorities.

The 52-year-old's lawyer maintains Donahue's innocence, saying: "He's not guilty. He denies the charges, and we will dispute it in court."

Police in the US arrested Donahue after "an extensive joint re-examination of the case" that began in 2015.

New technology was able to trace a lone yellow sock found at the crime scene back to the long-time suspect.

Ms Kulb's body was found in November 1991 in a wooded area of an undeveloped cul-de-sac about 40km southwest of Philadelphia.

Authorities believe the 27-year-old's body was moved there after she was killed.

During the search of Donahue's apartment in 1991, state troopers found a yellow sock that was similar to the one left at the crime scene, as well as a job application with Ms Kulb's name on it.

When the case was re-opened, the photos of the socks were enhanced so investigators could make the connection between Donahue's apartment and the crime scene.

Anthony Voci, the supervisor of the district attorney's homicide unit, said that the arrest "demonstrates our commitment to the ideal that there is no case, no amount of time, that we consider a lost cause".

Main image: Pennsylvania state troopers lead Theodore Dill Donahue out of the Pennsylvania State Police Troop K barracks in west Philadelphia after arresting him as a suspect in the 1991 murder of Denise Sharon Kulb | Image: Tim Tai/AP/Press Association Images