Juror after juror said Friday that Jason Van Dyke was not a good witness.
He was rehearsed, some said.
He was not believable, said a juror who identified herself as No. 245.
"I felt he shouldn't have" testified, she told Chicago reporters. "He messed up. His testimony wasn't credible to me."
The 12 jurors found Van Dyke, a Chicago police officer, guilty of second-degree murder and 16 counts -- one for each bullet -- of aggravated battery for the 2014 killing of Laquan McDonald.
One juror said of Van Dyke's testimony, "It was rehearsed. He had a lot of 'I don't know's."
Another said, "He was fumbling around trying to remember things. His memories and facts and other evidence didn't line up."
Van Dyke testified McDonald "turned his torso towards him" and raised his knife across his body. At that point, he shot him, Van Dyke said.
But prosecutor Jody Gleason challenged Van Dyke's account, pointing out one of several inconsistencies in his testimony. "You've sat here for several days and watched several videos. ... Have you ever seen Laquan McDonald do that on one of those videos?" she asked.
Van Dyke said the dashcam video of the shooting and an animated recreation of the shooting presented by the defense didn't show his perspective. But he acknowledged he didn't see McDonald raising the knife in the recreation.
Jurors watched the dashcam video multiple times, they said.
Juror 248 said it was the fact that it showed Van Dyke stepping forward toward McDonald instead of stepping back.
"We all pretty much thought he could have avoided it if he had retreated," she said.
She told reporters that the first thing the jury did was take an anonymous poll. Seven people thought he was guilty of murder, three were undecided and two thought Van Dyke was not guilty.
They came to a consensus Friday morning on second-degree murder, one juror said, because while they found Van Dyke thought he was doing the right thing, his actions were unreasonable.
"He should have realized what the situation was and instead of escalating the situation, he should have looked at other options," the juror said.
Jurors said they didn't feel race -- Van Dyke is white, McDonald was black -- was a factor in the decision.
"We didn't come here because of race we came here because of right and wrong," one said.