Their love was marked by sex, lies, and crime-scene tape.

On Monday, the romantic relationship that blossomed between Robertito Fontan, a married Philadelphia police officer, and Elizabeth Sanchez, a mother of three facing drug charges, landed one of them in prison.

U.S. District Judge R. Barclay Surrick sentenced Fontan, 42, a seven-year veteran of the narcotics squad, to a year behind bars for lying about his liaisons with Sanchez, who prosecutors said leaked sensitive information about an ongoing drug investigation.

"By all accounts, [Fontan] was a stellar officer and exceptional at undercover work," Assistant U.S. Attorney Neuman Leverett III wrote in a sentencing memo. Still, "his conduct in this case demonstrated little respect for the law he swore to uphold."

Fontan's sentence Monday came three months after a jury convicted him of three counts of lying to federal investigators.

To hear prosecutors tell it, his relationship with Sanchez, whom he met in 2003 outside a Philadelphia courtroom, was particularly star-crossed.

Not only was he an undercover narcotics officer and she an accused drug user, she had an ex - in this case, Jose Sanchez, a Kensington cocaine dealer Fontan was later in charge of investigating. (Jose and Elizabeth shared a last name but were not married.)

Fontan warned her to keep her distance, and she read between the lines, prosecutors said. That lapse had consequences in January 2008 during a cocaine buy the U.S. Drug Enforcement Administration set up with Jose Sanchez. Fontan, operating undercover, went to buy the drugs, but the cocaine dealer never showed. Elizabeth Sanchez had warned him.

FBI agents became involved once the DEA began to suspect a leak within its investigation. Despite repeated questioning, Fontan denied any relationship with Sanchez beyond that of a narcotics officer and an informant.

Fontan's lawyer, Jack McMahon, maintained that his client lied only because he was ashamed of cheating on his wife - who on Monday asked Surrick in her own testimony to spare her husband. He had already suffered since his arrest and lost a job he loved, she said.

In the end, McMahon argued, Fontan's slipup had minimal effect on the DEA investigation. Jose Sanchez was arrested, pleaded guilty to cocaine distribution charges, and is serving a 10-year prison term.

Fontan spent his career trying "to put drug dealers in jail for significant periods of time and was successful in doing that," McMahon said Monday.

Now, however, Fontan will be there, too.