PHOENIX -- Phoenix police detectives had evidence that could have helped them identify accused "Baseline Killer" Mark Goudeau nine months before his arrest, an investigator who worked on the case said.

Goudeau is accused of nine slayings and more than a dozen rapes and kidnappings.

The main piece of evidence Phoenix police used to arrest Goudeau in early September 2006 was DNA found at the scene of a double-rape.

In September 2005, two sisters were raped in South Phoenix, and police collected two swabs of evidence from the breasts of one of the women, hoping the rapist's DNA could be detected.

An investigator on that case said a specialist in the Phoenix police crime lab did a full DNA analysis on only one of the two swabs, and the test did not give investigators a suspect.

The investigator said his superiors told him the other swab was lost.

Over the next seven months, seven people were slain by the man popularly known as the "Baseline Killer."

After the ninth slaying, which occurred in June 2006, Phoenix police decided to ask the Arizona Department of Public Safety for help, an investigator said at the time.

Among the evidence DPS tested in its crime lab were both of the swabs taken from the sexual assault nine months earlier.

DPS analyzed the DNA on the second swab, and matched it to that of Goudeau, who was later arrested, charged and convicted of the double-rape.

Billy Coleman of the Phoenix Law Enforcement Association said he confronted his superiors about missing evidence.

"It is such a sad statement, but when I confronted a commander about this -- about items of evidence not tested that could have saved victims -- I was told we were fortunate that we lost that evidence before we sent it out because we would have consumed it and not had it," Coleman said.

Coleman would not say which case he was referring to, but a source in the Phoenix Police Department confirmed it was the Baseline Killer case.

When asked about the evidence, a Phoenix police public information officer offered a written statement explaining why the department turned to DPS for help.

According to the statement, police turned evidence over to the DPS lab to use DPS' more advanced DNA analysis technology.

The technology, known as Y-STR DNA testing, is a more accurate way of testing men's DNA.

DPS Lab Superintendent Todd Griffith said without Y-STR technology, it would have been difficult to find a suspect.

The DPS lab first started using the technology in April 2005 -- months before the rapes, robberies and slayings attributed to the Baseline Killer.

Nevertheless, Phoenix police Cmdr. Chuck Miiler said the case is not so simple.

"There is so much information involved (that) it's not factual to just say, 'Hey, seven additional homicides occurred, and they could have been prevented,'" Miiler said. "It's just not truthful in that light; there's just so many moving parts to this complex case."

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