But the lab results underpinning that finding were discredited two weeks ago, leading prosecutors to release the widow from jail more than two years after she was incarcerated for the supposed crime. Now, Cynthia Sommer wants the death certificate rewritten to show her husband wasn't murdered.

"What can they say, that I killed him with a hammer?" she told The Associated Press.

The San Diego County medical examiner's office won't say if it will change the cause of death. The district attorney's office says it may bring new charges if additional evidence is found but admits it has no case against the widow.

Sommer, 34, was convicted of murder in January 2007 after initial tests showed enormous amounts of arsenic in frozen samples of her husband's liver and kidney, despite concerns from the lab's own director and other experts.

 With no proof that the widow was the source of the arsenic, prosecutors relied heavily on circumstantial evidence of her financial debt and later spending sprees, including wild parties she threw after her husband's funeral and breast implants paid for with his $250,000 life insurance payout.

Prosecutors told jurors Sommer was the only person with a motive to kill the Marine, but the linchpin of the case was always the arsenic: Without it, there was no physical evidence that Todd Sommer was even killed.

As prosecutors prepared for a second trial, ordered by a judge who ruled that Sommer received inadequate representation, they asked another lab to analyze previously untouched specimens. The samples had been embedded in paraffin wax and sealed in a drawer at a military morgue for six years.

The tests showed no traces of poison.

"This is a major forensic foul-up," said William Thompson, chair of the department of criminology, law and society at University of California, Irvine. "It's CSI gone awry."

Todd Sommer's death in February 2002 was initially ruled a heart attack. In March 2003, a naval panel recommended sending frozen tissue samples for heavy-metals testing at the Armed Forces Institute of Pathology in Washington.

The tests found 1,020 times the normal amount of arsenic in his liver and 230 times the normal level in his kidney.

Yet red flags were raised about the poison long before Cynthia Sommer was charged in November 2005.

Jose Centeno, director of the military lab that performed the tests, wrote in a February 2005 e-mail to the medical examiner: "I initially thought that the tissue samples were contaminated during collection ... I don't have a good interpretation of these results."

At trial, Centeno testified that he put aside those concerns after testing on other slices of the Marine's liver and kidney by different labs also turned up high levels of arsenic.

Other medical experts were stumped that arsenic was not found in other body parts tested, including his brain, blood and urine. A professor at the University of California, San Diego, wrote prosecutors before trial that he was puzzled doctors didn't spot toxins when Todd Sommer visited a Marine clinic with symptoms of food poisoning days before his death.

Deputy District Attorney Laura Gunn shared the e-mail with Sommer's lawyers, who called expert witnesses to challenge the lab's handling of the tissues.

One juror said panelists told her after the trial that they overlooked doubts about the arsenic.

"They were annoyed the defense attorney brought up arsenic because otherwise why were we there?" said Lorie Cosio Azar, an alternate juror who testified on behalf of defense requests for a new trial. "They thought, `Of course there must be something wrong, there must have been a murder. We're here in the courthouse.'"

After the second trial was ordered, Sommer's new attorney demanded a list of all tissue samples.

Gunn said the samples were included on a list she gave Sommer's former attorneys in 2006, but she had ignored them because experts told her the preserved samples would be less reliable than the frozen ones already tested.

A spokesman for the military lab that did the original tests, Paul Stone, said the agency stands by its results.

District Attorney Bonnie Dumanis said the case shows the criminal justice system "is not perfect," but she wouldn't rule out filing new charges against the widow.

"Did the lab contaminate evidence? How did Todd really die?" Dumanis said. "Our office will continue its duty to seek the truth."

Naval investigators are treating the Marine's death as an open case.

"We have conflicting reports from labs and we have prosecutorial decisions that have yet to be made," said Ed Buice, a spokesman for the Naval Criminal Investigative Service. "The fact remains that we have a young, healthy Marine who died, so we want to figure out why if at all possible."

Sommer, a mother of four, is living with a cousin in Monterey, Calif. She has not spoken to her late husband's family since she was released April 17. Todd Sommer's father, Mitchell, declined comment.

Copyright 2008 Associated Press