It was the most conclusive testimony to date in the monthlong trial that puts a weapon in Hernandez's hand around the time of the slaying.
Hernandez is charged with murder in the killing of Odin Lloyd, who was dating the sister of Hernandez's fiancee. Lloyd was shot to death early on June 17, 2013, in an industrial park near Hernandez's home in North Attleborough. Lloyd sent his last text message at 3:23 a.m., and two witnesses have testified they heard loud bangs around that time. The murder weapon has never been found.
Kyle Aspinwall, a former New Hampshire police chief who now works for Glock, began his testimony Wednesday by showing jurors a Glock 21. The semiautomatic handgun uses .45-calibre bullets, and prosecutors have argued that based on ballistics evidence, a Glock 21 was the murder weapon.
As Aspinwall testified, prosecutor Patrick Bomberg played clips of video recorded by Hernandez's extensive home surveillance system June 17, as well as still photos taken from the videos.
At several points in the video, Hernandez can be seen carrying a black object in his hand. Hernandez's defence team has said the object could have been a TV remote or another electronic device.
But Aspinwall said his opinion was based on various characteristics of the weapon, including the curvature of back strap, the magazine well and trigger guard.
"In my opinion, the firearm shown in the video stills is a Glock pistol," he said.
The earliest clip played Wednesday was taken at around 12:45 a.m. before Hernandez leaves the house with co-defendants Carlos Ortiz and Ernest Wallace in a rental car. Prosecutors have said the three picked up Lloyd in Boston, then drove him back to North Attleborough.
Ortiz and Wallace are also charged with murder and have pleaded not guilty. They will be tried later.
Aspinwall testified that in the 12:45 a.m. clip, Hernandez can be seen switching a pistol from his right hand to his left as he walks through the living room.
Later, after Hernandez, Ortiz and Wallace return to the home at around 3:30 a.m., Hernandez can be seen outside the door to his basement. He faces the camera a few feet away while holding the object in front of him.
"This is a picture of the defendant holding what appears to be a handgun in his left hand in a reverse grip," Aspinwall said.
At various points in his testimony, Aspinwall stood and used his Glock to demonstrate how Hernandez was holding the weapon.
At around 2:30 p.m., less than 12 hours after the killing, other video shows Hernandez and Wallace hanging out by the pool before Hernandez gets a black object out of the rental car.
Aspinwall testified that the object appears to be the magazine of a gun.