D.C. police officer Richmond Phillips fatally shot his former mistress and then let their infant daughter "cook" in a car that had its windows rolled up on a hot spring day, Prince George's County's top prosecutor told a jury Monday.

Phillips' trial in the deaths of Wynetta Wright, 20, and Jaylin Wright, 11 months, is under way in Prince George's County Circuit Court. He is charged with two counts of first-degree murder, one count of child abuse resulting in death and a handgun charge. If convicted, he could be sentenced to life in prison without the possibility of parole.

During opening arguments, Prince George's County State's Attorney Angela Alsobrooks said that Phillips, 40, killed his former lover and their daughter because he did not want to pay child support.

Phillips and Wynetta Wright had met at a nightclub and engaged in a sexual relationship for several months. But the married police officer wanted nothing to do with his mistress when she told him she was pregnant, Alsobrooks said. After Jaylin's birth, Wynetta sought child support from Phillips, and a paternity hearing was scheduled.

The night before the May 2011 hearing, Wynetta, with her daughter in her car, met Phillips in a park near Prince George's County's border with the District. Phillips put a gun to Wynetta's head, shot her, and dragged her body to a wooded area, Alsobrooks said. He then drove Wynetta's car a short distance away.

Jaylin was left strapped inside in a baby seat. Phillips "allowed her, essentially, to cook in that car, hoping and praying that she would never be found," Alsobrooks said. The prosecutor said temperatures likely reached 125 degrees inside the vehicle.

Phillips' attorney, Brian Denton, said during his opening statement that his client did not commit the crime. "He didn't do this thing," Denton said. The evidence was circumstantial, he said, and the forensic work in the case was a "bit sloppy."

Phillips, who sported dreadlocks and wore a black suit in court, did undercover narcotics work as a vice officer in D.C.'s Metropolitan Police Department. He has been suspended without pay, a department spokeswoman said.

Wyvette Wright, Wynetta's mother, was one of the trial's early witnesses.

"She was a nice person," Wyvette said of her daughter. "She was into the police thing. She was trying to be a sheriff."

Jurors were given a summary of the evidence that prosecutors plan to present. Surveillance video and phone records show that Phillips was in the park on the night of the shooting, and the defendant's DNA was recovered from the victim's car, Alsobrooks said.

Phillips eventually admitted to being in the park on the night before the paternity hearing, Alsobrooks said. But when Prince George's County detectives interviewed him shortly after Wynetta and Jaylin were reported missing, he denied having had any contact with his former lover.

"I haven't seen her in over a year," Phillips said in a video of the interview played in court Monday.

The trial is expected to last about six days.