The jury trial of an MBTA operator who was at the controls of a Green Line trolley when it crashed into another train in July 2021 begins today in Brighton Municipal Court.

Owen Turner has been charged with gross negligence in causing the collision that left 24 passengers and three crew members injured and caused $2 million worth of damage to the trains.

The National Transportation Safety Board issued a preliminary report that found the Green Line train accelerated to a speed of 31 mph — three times the speed limit — along Commonwealth Avenue before colliding with another train that was moving at about 10 mph. In its final report issued last week, the NTSB revealed that Turner told investigators he can’t remember what happened and may have blacked out or fallen asleep after he saw the signal at St. Paul Street turn green, indicating he could proceed. Investigators said they could find no evidence that Turner was impaired by drugs, alcohol or a lack of sleep.

Rachael Rollins launched an investigation into the accident as one of her last acts as Suffolk County district attorney before she began her role as United States attorney for Massachusetts. She said Turner had a reputation for speeding and a history of violations. And indicated she wasn’t letting the MBTA off the hook.

“The MBTA had a duty to address its employee’s reckless behavior,” Rollins said in a press release announcing the investigation. “The agency failed to fulfill its legal obligation to take meaningful action in light of the real safety risk these acts created. We will be looking into whether the T’s behavior, or lack thereof, merits criminal action.”

As of now, there has been no word about anyone at the MBTA being charged in connection with the crash.