Robert Bates, charged with second-degree manslaughter in the April 2 killing of Eric Harris, pleaded not-guilty Tuesday. Bates and Tulsa sheriff’s department have maintained that the reserve deputy mistook his firearm for his Taser and fired the weapon at Harris accidentally.

Bates, 73, was part of a sting operation investigating illegal gun sales. In a video of the incident released by the Tulsa sheriff’s office last week, police can be seen pinning Harris, 44, to the ground before Bates shouts ‘Taser!” He then fires a single shot. But soon after, Bates realizes he fired his gun and can be heard saying, “I shot him. I’m sorry.” Bates was charged with second-degree manslaughter the day after the video’s release on April 12.

Tulsa Sheriff Stanley Glanz went on the defensive Monday against claims that the police department falsified Bates’ training records, dismissing the accusation and telling the New York Times that there was “no point in falsifying any records,” because he “could have waived all of those requirements” if he “felt like it.” He told the paper that he has waived training requirements in the past for reserves who have previously served as law enforcement; Bates last served as a full-time police officer more than 50 years ago. He went on to describe the reserve force as “essential to keeping the force at full strength”:

Mr. Bates was in the highest of three tiers of reserve deputies within the sheriff’s office, a position requiring more hours of training than lower levels, meaning that he could perform nearly all the duties of a full-time deputy, including making arrests. He was one of several deputies who formed a backup force for the undercover operation that snared Mr. Harris.

And although the sheriff’s department claims Bates received “extensive training” across his eight years as a reserve deputy, the Times reports Tulsa police have been “unable to produce most of the records” corroborating that assertion. As for the manslaughter charge, Glanz told the paper, “I agree with what the district attorney has done.”

Dan Smolen, a lawyer representing Harris’ family, argued in court Monday, the Associated Press reports, that the Tulsa sheriff’s office violated its own policies by allowing Bates to use his personal handgun on the job despite being trained to use a different weapon.

In a misty-eyed interview last Friday on the Today show, Bates, flanked by his family in his Oklahoma home, told Matt Lauer that shooting Harris was “number one on my list of things in my life that I regret.”

“I saw the light and I squeezed the trigger, and then realized. I dropped the gun,” he said. “This was not an intentional thing. I had no desire to ever take anyone’s life.”

This post has been updated to reflect that the Tulsa Sheriff’s Office is separate from the Tulsa Police Department. Image via Tulsa Sheriff’s Department. Contact the author at aleksander@gawker.com .