(ABCNEWS) — A District of Columbia police officer embroiled in a paternity suit fatally shot his mistress before leaving their infant child to “cook” in an overheated car, prosecutors said as the officer’s murder trial opened Monday.

Richmond Phillips committed the crimes because he was facing a paternity lawsuit and didn’t want to pay child support for a baby girl he fathered out of wedlock, prosecutor Angela Alsobrooks told the jury in her opening statement. A defense lawyer countered that his client “didn’t do this thing” and there wasn’t evidence for a conviction.

Phillips was arrested in June 2011 after police located the bodies of 20-year-old Wynetta Wright and her daughter, Jaylin, in a park outside Washington. Prosecutors say Phillips shot Wright and then drove the child — still strapped in the car seat of her mother’s car with the doors closed and the windows up — a short distance away where he left her to die.

Note: Read our discussion guidelines before commenting.