After an 18-month investigation, sheriff's officials turned their findings over to prosecutors, who decided there was insufficient evidence to charge Fitzpatrick. Deputy Dist. Atty. James Cosper, who reviewed the case, said the DNA sample taken from Fitzpatrick was "too weak" to conclusively show that he had had contact with the woman.
Cosper said Fitzpatrick's notebook did not contain the telephone number the victim said she wrote in it, but he noted that pages were missing.
The prosecutor also noted that the two deputies might have become aware they were the target of an investigation before internal affairs officers questioned them.
"This would have provided Fitzpatrick with the opportunity to wash his hands and remove the page with telephone number from his notebook," Cosper wrote.
"Such is speculation, however, and the fact of the matter is that evidence does not exist," he wrote.
Fitzpatrick was relieved of duty without pay last month after he pleaded not guilty to the charges stemming from the May 2008 encounters.
A preliminary hearing on whether there is adequate evidence to try Fitzpatrick is scheduled for July 6. He is free on $245,000 bail.