A District of Columbia police officer who killed his mistress and their young daughter was put on trial on Monday.

Richmond Phillips is accused of fatally shooting 20-year-old Wynetta Wright as well as leaving their 11-month-old daughter Jaylin Wright in a hot car which led to her death in June 2011.

Opening arguments started in the trial which is taking place at the Prince George's County Circuit Court where Phillips faces two counts of first-degree murder charges, one count of child abuse resulting in death and a handgun charge.

If Phillips is convicted, he could be sentenced to life in prison without the possibility of parole.

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

"He was either going to talk her out of that paternity suit or he was going to kill her," said Alsobrooks, according to Fox News.

The married police officer wanted nothing to do with his mistress when she told him that she was pregnant. 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 allegedly put a gun to Wynetta's head, shot her and dragged her body to a wooded area. He then drove Wynetta's car a short distance away and left Jaylin in the vehicle during the warm day with the windows rolled up.

"That baby cooked," Alsobrooks said, noting that there was a heat advisory on the day of the child's death.

Defense lawyer Brian Denton gave his opening statement that his client is innocent and that there is only circumstantial evidence against Phillips.

The officer was suspended without pay pending the outcome of the case which is expected to last through the week, according to The Associated Press.