How Cold Case Units Decide Which Files to Reopen

The National Institute of Justice defines a cold case as any case whose probative investigative leads have been exhausted, regardless of how much time has passed. Nothing in that definition is about age. A case can be cold after two years or still active after twenty. It moves again when a new lead exists, not because an anniversary arrives.

The backlog those units work from is large. In a 2019 article on cold case best practices, NIJ put the number of unresolved homicides in the United States from 1980 to 2016 at an estimated 242,000. It said roughly 40 percent of homicides go unsolved, and that the national homicide clearance rate fell from 78.3 percent in 1975 to 59.4 percent in 2016.

Reopening a case usually starts small. It is an inventory of what sits in evidence storage and a decision about what is worth sending back to the lab.

Which files go to the top of the pile

No unit can work every unsolved case at once. The NIJ guidance says to start with the investigations that have the most apparent means of resolution, and to weigh database hits, how easily a case could be resolved, and community interest when choosing. It lists the usual reasons a case becomes workable again: advances in forensic technology, growth in DNA and other databases, changes in relationships over time, a fresh review that turns up something missed, and renewed public attention.

In practice that means a file with untested biological evidence still in storage tends to move ahead of a file where the evidence was lost or never collected. Samples once thought unusable have later produced DNA profiles. A swab the lab of 1995 could not read may be readable today.

Paying for the lab

Funding decides which of those samples actually get tested. NIJ issued its first solicitation for a grant program called Solving Cold Cases with DNA in July 2004. In 2005 it awarded $14.2 million to 38 state and local agencies, and in 2007 more than $8 million to another 21. The money paid for personnel and overtime, laboratory equipment and supplies, investigative travel, training, and outsourcing samples to private DNA labs.

A small department with a handful of unsolved homicides usually cannot absorb that cost on its own. A grant can be the practical event that brings a stack of old files back to a working desk.

The Rasmussen file goes cold

The murder of Sherri Rasmussen shows each of those conditions in one case. On February 24, 1986, Rasmussen, a nursing director, was found beaten and shot three times in the Van Nuys condominium she shared with her husband, John Ruetten. The Los Angeles Police Department treated it as a burglary gone wrong.

Detectives Lyle Mayer and Steve Hooks noticed things that did not fit, including a bite mark on Rasmussen's arm. Hooks found it unusual, reasoning that bites in a struggle are more often inflicted by women, while most burglars are men. The burglary theory stood anyway, and the investigation stalled within months.

Rasmussen's father, Nels, told police he suspected Stephanie Lazarus, an LAPD officer who had dated Ruetten before his marriage. Mayer told him there was nothing there. The case sat for more than two decades.

A missing swab

In the late 1990s the LAPD set up a unit to go through evidence in unsolved cases and decide what might yield new leads through DNA testing. In 2004, criminalist Jennifer Francis turned to the swab taken from the bite mark. It was missing from the property log. It turned up only after a search of the coroner's freezers; samples that old had never been entered in the computer system.

Francis found no match in CODIS, the FBI's DNA index. But the saliva on the swab came from a woman, which undercut the burglary theory. When she asked the supervising detective whether the female officer had been looked at, he insisted it was a burglary. The result went back into the file.

Fresh eyes

In March 2008, Van Nuys homicide detective Jim Nuttall found a box near his desk holding two old case files. One was Rasmussen's. He and his partner, Pete Barba, read the female DNA result and treated the case as a murder with a staged burglary.

The file supported that. Rasmussen's jewelry box sat in plain view, untouched. The condo was inside a gated complex. The front door had not been forced. A stack of stereo equipment at the foot of the stairs had a bloodstain shaped like a thumb but no print, suggesting gloves, and the blood was Rasmussen's, suggesting the equipment was stacked after the struggle.

The detectives built a list of female suspects and eliminated all but Lazarus, by then a detective in the department's art theft unit. Investigators collected a cup she threw away while off duty at a Costco in Simi Valley. DNA from it matched the bite mark.

The arrest and the confession

In June 2009, Robbery-Homicide detectives Greg Stearns and Dan Jaramillo asked Lazarus to come to the jail at Parker Center to help with an art theft matter. After she checked her gun and sat down, they told her they wanted to talk about Rasmussen. She said she recalled little, then showed more knowledge of the case, then accused her colleagues of treating her as a suspect. Asked for a DNA sample, she said she needed to talk to someone and left the room. She was arrested outside it.

At trial in 2012, prosecutors argued her motive was jealousy over Ruetten's marriage. In March 2012 the jury convicted her of first-degree murder, and she was sentenced to 27 years to life. At a parole hearing in November 2023 she admitted the killing for the first time, and a commissioner found her suitable for release. The full parole board rescinded that decision on October 2, 2024, after Gov. Gavin Newsom raised concerns. At a new hearing on February 12, 2025, parole was denied. She is next eligible in 2028.

What clearance numbers do and do not show

Clearance rates have recovered from their low. The FBI's estimate for 2022 was 52.3 percent, the lowest it had ever reported. It rose to 61.4 percent in 2024, and the Murder Accountability Project reported in August 2026 that FBI estimates put 2025 at 68.8 percent, the largest one-year improvement on record and the best rate in a quarter century.

One detail in how the FBI counts these matters for cold cases. Clearances are recorded in the year the case is cleared, and some of them pertain to offenses from earlier years. An arrest in 2026 for a 1985 killing counts toward 2026. A department that clears a batch of old cases can lift its current rate even while recent cases stay open, so the published number does not cleanly separate fresh work from cold case work.

Most reopened cases do not end in an arrest. A reopening is a set of conditions lining up: the evidence still exists, a method exists to read it, money exists to pay for the test, and a database turns the result into a name. In the Rasmussen case, the evidence and the method to read it were in place by 2004, and the result pointed to a woman. What was missing was someone willing to follow it, and that took four more years and a box left near a detective's desk.

Sources

1. NIJ: Cold Cases, Resources for Agencies, Resolution for Families (NIJ Journal 260, 2008)
2. NIJ: Expert panel issues new best practices guide for cold case investigations (Sept. 2019)
3. Murder of Sherri Rasmussen - Wikipedia
4. NBC News: Ex-LAPD detective who hid murder for decades won't be paroled, reversing earlier decision (Oct. 2024)
5. CBS Los Angeles: Stephanie Lazarus has parole denied again (Feb. 12, 2025)
6. Murder Accountability Project: Here's the reason for America's good news about murder (Aug. 24, 2026)
7. FBI Uniform Crime Reporting: Clearances (Crime in the United States 2018)

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