This would probably be a long shot but since they have DNA that might be able to find a suspect i would encourage police to look into serial killer David Misch who committed many crimes including the murders of two best friends.
David Misch and his crimes timeline
1977: Misch, then 16, breaks into a neighbor's house and rapes the household maid (at knifepoint).
1978: Paroled for this crime. Not sure what month he was paroled
February 1979: Arrested for false imprisonment and assault with a deadly weapon (later charged with assault with intent to commit rape). Released just months later in September on parole.
July 1982: Convicted of beating a woman at knifepoint. Amazingly, he is paroled again in January 1984.
1985: Arrested for indecent exposure after he was found to be driving around naked in Oakland.
1986: Was under suspicion for several drug and burglary incidents, diversion court was being considered.
February 1986: Murders Michelle Xavier and Jennifer Duey by shooting and strangulation. Rape also occurred, according to the police. Misch isn't charged until much later for this case.
May 1988: Convicted of burglary and given a sentence of one year plus one year of probation. Paroled in October-November 1988.
November 19, 1988: Michaela Garecht is abducted from the Rainbow Market parking lot in Hayward, CA.
November 21-25, 1988: Arrested for drug possession.
November 17, 1989: Paroled for the drug possession charges.
December 1989: Murders Margaret Ball. The crime is horrific: Ball was found in a fetal possession laying on a butcher's knife that she had been stabbed with numerous times, and she was beaten so badly that Misch knocked out one of Ball's teeth.
1990: Convicted of Ball's murder. Receives a term of 18 years to life in prison.
2006: Denied parole.
2009: Denied parole for a second time.
2018: Charged with the Duey and Xavier homicides.
December 21, 2020: Charged with murder in the presumed death of Michaela Garecht.