SANTEE, Calif. -- Thomas Sadler, a veteran sheriff's detective accused of sexually assaulting a prostitute while on duty, and who went missing Wednesday night before turning up Thursday morning, has waived his right to a preliminary hearing so his case can proceed straight to trial. A readiness conference is set for May 12; the trial is scheduled for May 18.

Sadler, 48, was reported missing by his wife after he failed to return home from a walk near Carlton Hills and Mast boulevards in Santee around 12:30 p.m. Wednesday, San Diego County sheriff's Sgt. Brent Strahm said.

He returned home on his own, unharmed, around 7:45 a.m. Thursday, according to sheriff's Sgt. Tom Poulin, who said Sadler apparently slept overnight in a neighbor's backyard.

Poulin said that Sadler indicated he would be going to his preliminary hearing scheduled for 8:15 a.m.

Late Wednesday afternoon, Sadler's wife, Adrianna Sadler, told deputies her husband frequently takes walks and this time, took his wallet and prescription medication but left his cell phone and keys, which was "highly unusual," according to Strahm.

"[She believed] Thomas Sadler [was] depressed and was also very concerned about statements he made to her around 2 a.m. the previous morning, which led her to believe that he might try to harm himself," Strahm said.

Sadler, a 23-year veteran of the sheriff's department, is charged with five felony charges, including sexual battery by restraint. He faces about eight years behind bars if convicted, according to the District Attorney's Office.

After his arrest last July, Sadler was hospitalized for trying to commit suicide while in custody.

Sadler has been on administrative leave pending the outcome of the charges against him. According to a declaration filed in support of an arrest warrant, the charges stem from a Feb. 6, 2008 incident.

The declaration states that a prostitute in her 20s was sitting on a curb in the 3100 block of El Cajon Boulevard in the North Park area when Sadler, driving his unmarked work vehicle, pulled up alongside her and identified himself as a "sheriff's officer."

He then allegedly forced the woman into his vehicle and drove her to the 2800 block of Camino del Rio South, where he pulled over on the edge of a restaurant parking lot and forcefully fondled her, according to the declaration.

Three witnesses called 911 to report what they took to be a kidnapping in progress, but Sadler fled before police arrive, according to the court filing.

Sadler was accused of similar behavior in 2002 in a lawsuit filed in federal court. A 34-year-old woman, Nicole Bowman, said Sadler stopped her in a parking lot after she had left a bar, then searched her, pulling up her bra and looking down her pants. The county settled the lawsuit with Bowman for $10,000, according to court documents.

Michael Berg, Sadler's attorney, said his client decided to waive his preliminary hearing after the prosecutor indicated he may add a more serious charge of kidnapping. Berg said the prosecutors will most likely not consider filing the charge.

Sadler could go to prison for eight years if he's convicted of all five felonies.

From around 5 to 11 p.m. Wednesday, sheriff's officials searched the Santee area for Sadler using a helicopter, tracking dogs and search and rescue ground teams but no leads were found, Strahm said.