For more than three decades, a potentially crucial clue to the identity of a serial killer who terrorized Denver-area residents has sat in an evidence locker, unknown to possible witnesses.

But now, a law enforcement officer has released details to The Denver Post that he believes should have been shared years ago as part of the effort to find the killer. And officials now say they will submit the evidence to a forensic lab for re-examination.

An Aurora woman who was left for dead but survived one of the attacks says it’s about time.

“I can’t understand why it hasn’t been released,” said Donna Holm, 59. “You just never know it could be what police need to solve the case.”

The evidence was found in one of the 1984 attacks that left four people dead, including 7-year-old Melissa Bennett.

When the killer lifted Melissa’s blood-drenched body from her bed, letters embroidered on his shirt were transferred in blood onto the girl’s pajama top. Investigators believe the fuzzy letters likely identify the killer’s name or the business where he worked.

The release of the evidence is opposed by a prosecutor, a detective who worked on the case in 1984 and for two decades afterward, and the current cold case detective tasked with solving the mystery. There is also a debate about what the letters actually say.

“It could hurt the case more than it could help it,” said Marv Brandt, who began investigating the case with other Aurora detectives the day it was discovered. The Aurora Police Department could be inundated with bad tips, he said.

Melissa and the three other murder victims, including her parents, Bruce and Debra, ages 27 and 26, respectively, were murdered by a hammer- and knife-wielding rapist and killer in January 1984. Holm and Melissa’s 4-year-old sister, Vanessa, were left for dead with permanent head injuries.

Holm said the letters could identify the serial killer.

The law enforcement source said he believes that through today’s social media, the clue might help solve the case. Someone may know who or what business the letters identify, he said. Deciphering letters“What happens if you wait 50 years before revealing the clue: Everyone is dead including the suspect,” said the official, who spoke on condition of anonymity because he is not authorized to release information about the evidence.

He said he is haunted by the memory of a black-and-white crime-scene photograph of Melissa in pajamas with a design of a heart next to the killer’s inadvertent, bloody moniker. The heart seems to point below to the upside-down letters.

“No one thought it was a good idea to confirm or deny information on any physical evidence issues,” Aurora cold case Detective Steve Conner wrote in an e-mail to The Post.

Brandt, who now works as a cold case investigator for the Arapahoe County Sheriff’s Office, said the killer likely is unaware that he left such a clue, and if presented to him during an interview, it might be difficult for him to explain it away. Releasing the clue could tip him off and prepare him to have an explanation ready, Brandt said.

Assistant District Attorney Mark Hurlbert said the primary reason the letters were never released is because “it’s not definitive evidence.” In fact, there were two different interpretations of what the letters say, one by the Arizona Department of Public Safety and another by the Royal Canadian Mounted Police, he said.

The Arizona lab indicated the letters are “RICHAR.” The Canadian experts deciphering the same blood impression indicated the letters most likely spell out “PETAW–C.” The first three letters were more definitive, the Canadian crime report says, according to the source.

There were at least two gaps in the name or business tag because of folds in the pajama top, making some letters indecipherable.

Both Conner and the source say they saw only the Canadian report.

Initially, the Arizona lab seemed to verify a suspect in the case, who had a first name of Richard. But years later that suspect was cleared through DNA evidence, Hurlbert said.

Hurlbert, Brandt and the source all say Melissa’s pajama top should be re-examined with modern equipment to obtain a more definitive interpretation of the letters.

Hurlbert said he will meet with Conner and ask him to request a forensic analysis.

A connectionHolm, who was 28 at the time and working as a flight attendant, was attacked after pulling into her garage on the evening of Jan. 9, 1984. Her attacker or attackers struck her in the left temple, stripped her clothes off and raped her on the concrete garage floor.

“He beat my head against the wheel well,” Holm said.

The next day, a killer struck 50-year-old Patricia Smith in the head with a hammer in her townhome at 12610 W. Bayaud Ave. in Lakewood.

On Jan. 16, 1984, a week after Holm was attacked, a hammer-wielding killer entered the home of Bruce and Debra Bennett and murdered the couple and their daughter, Melissa. They lived at 16387 E. Center Drive in Aurora.

After killing her parents, the killer entered Melissa’s bedroom, struck her in the head with a hammer, soaking her sheets and pajama top in blood, picked her up, laid her on the floor and raped the child. At the time, Lakewood and Aurora police speculated that whoever killed Patricia had also attacked Holm and murdered the Bennetts. Shoe prints left outside the Bennett household matched some found outside Holm’s house.

All three homes were only a few blocks away from Alameda Avenue. In 1984, new-home construction was booming in the two suburbs.

In 2010, DNA tests established a link between the Patricia Smith murder and the attacks on the Bennetts.

Holm said that after she was bashed in the head with a sledgehammer, she had to relearn how to talk. Holm often considers how fortunate she was to survive a brutal assault and has hoped for a resolution.

“It would be nice to close this chapter in my life,” Holm said. “To have people held accountable for what they did.”

Kirk Mitchell: 303-954-1206, kmitchell@denverpost.com or twitter.com/kirkmitchell, denverpost.com/coldcases