It looked bad for homeless alcoholic Lukis Anderson when DNA evidence tied him to a Silicon Valley millionaire's 2012 murder.

But when Anderson's lawyer proved that paramedics who had treated him on the streets of downtown San Jose inadvertently transferred his DNA to the Monte Sereno murder scene, she didn't just clear him. The case is believed to be the first in California and perhaps the nation in which DNA evidence was shown to have falsely placed an innocent person at the scene of a crime, lending credibility to defense lawyers who struggle to convince jurors to view DNA evidence more skeptically.

"Before, we just had hypotheticals, stuff that DAs would say was smoke and mirrors," said Deputy Public Defender Kelley Kulick, who handled the groundbreaking case. "Now, there is a case to support it."

Among defendants now pointing to Anderson's case in hope of clearing their own names are former Santa Clara County Supervisor George Shirakawa Jr., whose lawyers are challenging felony criminal charges that he was behind a fraudulent campaign mailer allegedly bearing his DNA on the stamp.

While others accused of a crime -- most famously exchange student Amanda Knox -- have used the so-called transference defense against DNA evidence with some success, those defendants weren't able to prove, as Anderson's attorneys did by establishing his alibi, that the DNA evidence had been compromised.

In the pivotal case, Anderson was arrested on murder charges after his DNA was found under the fingernail of Silicon Valley millionaire Ravi Kumra, who suffocated after thieves bound him during a 2012 home-invasion robbery at his gated Monte Sereno estate.

Despite the DNA, nagging concerns about the case persisted. The prosecution saw connections to support the DNA link -- that Anderson had a residential burglary conviction on a criminal rap sheet composed otherwise of nonviolent minor crimes such as being drunk in public, and he had spent time in the same jail dorm with a member of one of the gangs tied to the Kumra killing. But that gang member wasn't implicated in the murder. And while the others accused in the homicide belong to some of Oakland's most violent home-invasion gangs, Anderson didn't seem mentally capable of organized crime. He suffered a brain injury from being hit by a truck and could not even recall his whereabouts that November night.

Kulick pursued every avenue to prove Anderson had nothing to do with the crime, eventually discovering medical records that show on the night Kumra died, Anderson was at Santa Clara Valley Medical Center, where he had been taken by ambulance after passing out drunk in downtown San Jose.

His DNA turned up at the murder scene only because paramedics inadvertently transferred it there, via a simple oxygen-monitoring probe they'd clipped first onto his finger and then onto the dead man's. Prosecutors dropped the charges after examining a dossier Kulick put together, interviewing the paramedics and hospital personnel, and reviewing videotape of the crime scene to make sure the paramedics had really treated both men. Anderson walked out of jail five months later.

With the tacit support of the District Attorney's Office, Kulick plans to petition a judge to wipe the Kumra murder arrest off Anderson's record via a document declaring him factually innocent. It's expected to be granted, paving the way for more defense attorneys to tout the example, using the document, at a time when DNA is playing a key role in an increasing number and variety of cases, not just rape or murder. In the near future, for instance, DNA will be immediately tested at the crime scene, using portable equipment that has already been developed in the lab.

Of course, the Anderson case alone won't be a magic bullet, both in instances where there's plenty of other evidence, and if prosecutors successfully argue the incident is an unlikely chance occurrence. The California District Attorneys Association declined to comment. In a Sacramento baby-killing trial in March, for instance, lawyer Ruth Edelstein tried to sway a jury by recounting the case, but the panel came back with a guilty verdict anyway, based in part on evidence of an alleged admission to an acquaintance. Even so, Edelstein still plans to tell other juries about Anderson.

"Because of "CSI" and a lot of other misinformation, there's a belief that if someone's DNA is there, the person was there," Edelstein said, referring to the popular TV crime drama about forensic scientists. "But the presence of DNA doesn't tell you anything about how it got there."

Before the Anderson incident, the transference argument helped defendants get off the hook in at least two high-profile cases. In Italy, an appellate court last year overturned American exchange student Knox's murder conviction in the killing of her British roommate. The defense argued that trace amounts of DNA from both the victim and Knox that were found on a knife in Knox's boyfriend's apartment could have been transferred there by Knox, who lived with the victim and was in constant contact with her. A higher Italian court, however, has reversed that decision, concluding that the slain woman's injuries suggested multiple killers.

In 2012, an English cabdriver charged with killing a prostitute based on the discovery of his DNA under her fingernails was cleared after the defense argued that he had a dry skin condition -- so severe that his nickname was "Flaky." The defense successfully contended that his DNA could have been transferred to change he gave a passenger, who later killed her.

Scientists and cops have long recognized the risk of DNA contamination -- by lab technicians, for instance -- and of transfers from one object or person to the crime scene. Law Enforcement magazine, a trade publication, even warned officers two years ago to "take great care in collecting evidence if you have a sunburn or dandruff because your DNA may fall into the evidence." In the lab, one experiment showed that it only takes 30 seconds of handling something or someone firmly for skin cells containing DNA to be transferred. Another study demonstrated that semen on one garment can contaminate another if they are washed together in the same machine.

But with Anderson, there are actual medical records proving his innocence. In Shirakawa's case, defense attorney Jay Rorty has asked a judge for those records. He's also consulted with San Francisco lawyer Bicka Barlow, who specializes in DNA and is familiar with the Anderson case, according to court documents. Rorty declined to comment.

Exactly how Shirakawa's defense would claim a transfer occurred is unknown, but there are any number of possibilities -- for instance, if Shirakawa shook hands with someone who subsequently stuck the self-adhesive stamp on the mailer.

"You could very innocently come in contact with an object, and days or months later, your DNA shows up at a crime scene you had nothing to do with," said Barlow, speaking in general, not about Shirakawa.

Prosecutors are dead set against releasing Anderson's records to Shirakawa's lawyers. They argue Anderson's DNA records are confidential, "wholly" unrelated to the case and not potentially exculpatory. If the judge agrees, the jury could still hear about the case indirectly via the testimony of an expert defense witness. Prosecutor John Chase said either way he's confident he'll prevail.

But the Anderson episode is shifting the legal landscape by forcing the prosecution in cases that rest heavily on DNA to make doubly sure there's plenty of supporting evidence, Chase said.

"It's an absolute now," Chase said. "You can't make a case solely on contact DNA."

Contact Tracey Kaplan at 408-278-3482. Follow her at Twitter.com/tkaplanreport