That night, a Saturday, 42-year-old Lori Levinson was out on a date that ended badly at about midnight.
Three hours into his shift, about 1 a.m., the 25-year-old officer came upon Levinson in her Honda SUV at the intersection of 21st Street and Chandler Boulevard in Ahwatukee. He arrested her for drunken driving.
An hour later, as they pulled into the police station, Levinson accused Dirks of forcing her to have anal sex during the traffic stop.
Dirks said then -- and he continues to insist to this day -- that he did nothing of the sort.
But three years later, the repercussions of whatever did happen on that chilly February night still are being felt.
Shawn Dirks lost his career.
Lori Levinson says she's been plagued by continuing mental problems and alcoholism.
Dirks, who never was charged criminally, is a defendant in a pending civil lawsuit that Levinson filed in Maricopa County against him, his wife, and the City of Phoenix.
All but one piece of evidence strongly suggests that Levinson -- a four-time divorcée with a long history of accusing men of sexually assaulting her -- is lying.
But that piece of evidence, as controversial as it has become, is a doozie: In June 2001, a local police crime lab said it found a speck of Lori Levinson's DNA on the base of Shawn Dirks' penis.
But for the existence of what amounts to a microscopic bit of DNA that one expert has called "inconclusive," the allegations against Dirks would have vaporized.
However, to the Phoenix police and to the Levinson legal camp, the tiny swipe of DNA is proof positive that Levinson and Dirks engaged in sexual contact of some kind.
Says Levinson's attorney, Mark Breyer, who has funded her civil case for two years: "If two people are alone together and they both deny having sex, but the woman's DNA ends up on the man's penis, nobody's going to believe they didn't have sex. And in this case, the woman -- my client -- says the man raped her, and I believe her."
As Shawn Dirks tells the story, he was on routine patrol in the early morning hours of February 18, 2001, when he spotted the white Honda SUV at the Ahwatukee intersection. Its motor was running, the right blinker was on, and the headlights were off. But Dirks says he couldn't see a driver as he pulled behind the vehicle. He turned on his strobe lights and spotlight, and approached the vehicle on foot.
When he looked into the driver's window, Dirks saw a woman slumped in the front seat, apparently asleep. It was Lori Levinson.
Levinson appeared disoriented and disheveled when she came to, and he could smell alcohol on her breath when she finally opened her door to hand him her driver's license.
Dirks told Levinson to stay put, and he stepped back to his squad car, where he radioed in her license information. When he returned to Levinson's SUV a few minutes later, she was speaking to someone on her cell phone.
She asked Dirks to speak to the other party, whom she said was her FBI agent boyfriend. Dirks then talked for a minute or so with Bill Hanchak, a Phoenix FBI agent.
Hanchak later confirmed he'd told Dirks that he'd been on a date with Levinson that evening, but things had ended badly around midnight. Before hanging up, Hanchak also said Levinson had been drinking heavily.
But Levinson refused to take a field sobriety test at the intersection, and continued to be uncooperative.
From his squad car a few minutes later, Dirks sent a message for assistance to Phil Marriner -- the only other officer on duty in Ahwatukee that night. Officer Marriner responded within minutes.
After speaking by phone with a sergeant, the pair decided to arrest Levinson for DUI.
With some effort, the two officers pulled the obstructive Levinson out of the car, handcuffed her, and put her in the back of Dirks' cruiser.
Dirks then escorted the woman to the South Mountain precinct, 17 miles away. During the 22-minute trip, Dirks says, Levinson repeatedly asked him where they were going, and kept scooting around the back seat, even disappearing beneath his view now and then.
When they pulled into the station, Levinson demanded that Dirks get a female officer and a video camera. The rookie walked over and informed another cop that something was up with his DUI suspect.