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(CNN) —  

In 1991 Denise Sharon Kulb’s body was found in a woodsy, undeveloped cul-de-sac in suburban Philadelphia after being missing for over three weeks.

It took 28 years, but authorities have finally arrested someone in her killing – her then-boyfriend, thanks in part to new technology and a pair of socks.

Theodore Dill Donahue was arrested for the 1991 slaying of his girlfriend.
Theodore Dill Donahue was arrested for the 1991 slaying of his girlfriend.
PHOTO: WPVI

Theodore Dill Donahue, 52, was arrested in Kulb’s death after police gathered new evidence and interviews, Philadelphia District Attorney Larry Krasner and the Pennsylvania State Police said Tuesday.

Donahue was charged with murder, abuse of a corpse, tampering with evidence, obstruction of justice and false reports to police. He has pleaded not guilty.

Authorities began to reinvestigate Kulb’s killing in 2015, using new investigative tools to rebuild the case, Krasner said.

One of the methods used was photo-enhancing technology that linked a yellow sock found at the crime scene to a similar sock found at Donahue’s apartment in 1991. After this analysis, investigators determined they were a matching pair of socks, said Anthony Voci, supervisor of the District Attorney’s Office Homicide Unit.

Kulb, 27, was found dead in November 1991 in an undeveloped part of Delaware County, Pennsylvania. Her body was decomposed and dressed only in a sweater, with the rest of her clothing piled on top of her, according to the district attorney.

“Twenty-eight years ago, Denise Sharon Kulb was found dead in a remote area in the suburbs, abandoned and discarded,” Krasner said. “She was a mother, a daughter, a sister, a friend. She deserved far better than to be killed and left in a location unknown to those who mourned her.”

“We are determined to help deliver closure and some peace of mind to those who have waited for a resolution of this criminal investigation for nearly 30 years,” he added.

Donahue appeared in court Wednesday morning for an arraignment and pleaded not guilty, said his attorney, R. Emmett Madden. He is being held without bail.

“He is innocent, and we look forward to proving his innocence in court,” Madden said.

Investigators say that when they originally interviewed Donahue, he said the last time he saw her was during a drug-fueled incident. Donahue told them he and Kulb had purchased and ingested crack cocaine before being robbed at knifepoint. Kulb ran to get help, and he never saw her again, he said.

But when reinterviewed in 2015, Donahue gave a different story about seeing her at a bar and admitted he had lied before, officials said. Kulb’s sister also said that on the day of Kulb’s disappearance – October 19, 1991 – she had seen the couple fighting outside a bar where her sister worked, according to the district attorney.

Over the past four years, Pennsylvania State Police said they conducted multiple interviews with Donahue and other potential witnesses that suggested Donahue might have taken part in the murder. Voci, the prosecutor, said Donahue told multiple people over the past 28 years that Kulb was murdered in his apartment, which ultimately helped lead to his arrest.

“We are never finished investigating any case, as I like to tell people,” Voci said.

The interviews “also recreated Donahue’s retelling of how his old girlfriend was found face-down in the woods strangled to death, revealing details that no one but an eyewitness to the crime scene or the perpetrator should have known,” the district attorney’s statement said.

Police also said Donahue also acknowledged his nickname was “Ted Bundy” during interviews in 1991.

CNN has reached out to Kulb’s family for comment.