DALLAS -- A former Dallas police officer is on trial for negligent homicide.

Four years ago, Dallas Police Officer Bryan Burgess and his partner Michael Puckett were on patrol in south Dallas. 

“What were they doing that night? They were doing their jobs,” said defense attorney Robert Rogers.

The officers say they spotted 51-year-old Fred Bradford riding his bike without a helmet and lights a violation of city ordinance. They were going to stop him. Before they could pull him over, they claim they saw him reach into a car, which looked liked like he was making a drug transaction.

They ordered him to stop, but they say he took off.

“At that point, the evidence is going to show that Mr. Burgess made a series of decisions, which ultimately lead to Mr. Bradford's death,” said prosecutor George Solis.

Prosecutors say while Officer Puckett chased Bradford on foot officer, Burgess followed in his car. At some point, Burgess and Bradford crashed into each other.

"Mr. Burgess was following too closely and unable to stop to avoid the collision,” said Solis.

“He could not avoid it because Fred Bradford lost control and slammed into Officer Burgess car,” said Rogers.

An accident investigator testified Burgess was only going 11 miles per hour and was not negligent. The officers say the victim was cursing at them and did not look like he had severe injuries.

Prosecutors say Bradford had a broken back and broken ribs. He died three weeks after the accident.

Burgess is accused of lying to investigators at the scene and moving his squad car and the bicycle.

Puckett took the stand this morning. He was asked who moved the bike.

“Officer Burgess. He moved it next to the street and squad car. Do you know why he did that? No sir."

Defense attorneys say Burgess moved the squad car and bike so Dallas Fire Rescue could get to the victim quicker.

Prosecutors say Burgess was an overly aggressive officer who had been repeatedly warned about policy violations.

Defense attorneys say he was a good officer trying to prevent crimes and protecting the public.