Paula Vance, 41, had been found raped and strangled in February 1998, her partially nude body dumped behind a downtown business.
Five security cameras had captured portions of the brutal crime. But just before the suspect came fully into view, the closest camera cut away.
"Basically, it was little more than a silhouette and it was extremely frustrating," Shepard said. "In another second [of footage], we would have had a great shot of his face and we might have been able to identify him."
The seven-member cold-case unit that Shepard joined was charged with reviewing a huge backlog of unsolved killings that occurred from 1960 to 1997, with an emphasis on sexually motivated murders.
The Vance murder fit the unit's mandate, so Shepard decided to send off semen recovered from the victim to the LAPD's crime lab to see if DNA evidence suggested a link with any known criminal. It did.
In the months that followed, Shepard developed DNA evidence suggesting that the Vance case, along with at least 11 other murders, could be laid at the feet of a man police now suspect is one of the city's most prolific serial killers, convicted rapist and onetime pizza deliveryman Chester Dwayne Turner, 37.
And in the process of developing evidence against Turner, Shepard was able to clear a man who had been wrongly convicted of at least two of the murders. David Allen Jones, a part-time janitor with the mental capacity of an 8-year-old, was released from state prison in March after serving more than 11 years.
"What's unusual here is that after he had his man and after he had found crimes that Mr. Jones could not have done, he took that extra step," said Jones' attorney, Gigi Gordon.
"He suspended his own disbelief that such a mistake could happen and pursued it. And for that, Mr. Jones and I have nothing but gratitude for him," Gordon said.
Colleagues say the case is vintage Shepard, a soft-spoken Missouri native and Army veteran described as methodical, tenacious and, at times, after 30 years with the LAPD, a bit crusty.
"He has amazing recall for every detail of a case," said Det. Dave Lambkin, who heads the cold-case homicide unit. "Even on the most complex case, he can recall virtually any aspect of it, whether it's dates or times, places or names."
As a patrol officer in the 1980s, Shepard was working beats in South Los Angeles and heard detectives discussing serial killers preying on women, many of them prostitutes and street people.
"The division's homicide detectives believed there were multiple serial murderers working in the area," Shepard said. "But we never received a lot of information about what to look for. They never developed a suspect description."
Years later, when the Vance case landed in his lap, Shepard considered whether the murder could be the work of a serial killer. But he had little to work with.
With his then-partner Jay Moberly, Shepard scoured the streets for registered sex offenders, distributed fliers and sent teletypes out to all of the LAPD divisions describing the crime.
He asked for help from the LAPD's crime lab and sought advice from colleagues in the Robbery-Homicide Division's rape special section.
Shepard had the security camera image enlarged and even went to Paramount Studios seeking help in deciphering the image.
Hopes for a break in the case brightened briefly when police detained a Hollywood man who fit a general description of the suspect. But he was eliminated by DNA testing, technology that eventually would play a key role in the case.