Video report by ITV News Washington Correspondent Robert Moore
David Pleoger testified on Thursday at the trial of since-fired officer Derek Chauvin, who is charged with murder and manslaughter in Mr Floyd’s death.
He acknowledged officers are trained to roll people on their side to help with their breathing after they have been restrained in the prone position.
"When Mr Floyd was no longer offering up any resistance to the officers, they could have ended the restraint," Mr Pleoger said.
Prosecutor Steve Schleicher then asked: "And that was after he was handcuffed and on the ground and no longer resistant?"
"Correct," replied Mr Ploeger, who is now retired from the force.
Former police officer Chauvin is on trial, accused of killing Mr Floyd, a 46-year-old black man, while arresting him in Minneapolis, US.
Jurors were shown on the first day of the trial a video of the officer pressing his knee on Mr Floyd's neck for several minutes as onlookers yelled at him to get off.George Floyd's death triggered large protests around the US, scattered violence and widespread soul-searching over racism and police brutality.
The most serious charge against Chauvin carries up to 40 years in prison.
Thursday’s testimony began with Floyd's girlfriend, Courteney Ross, tearfully telling the jury how the pair first met in 2017.
She said they met at a Salvation Army shelter where he was a security guard with "this great, deep Southern voice, raspy".
Ms Ross also spoke of how they had both struggled with an addiction to painkillers.
“Our story, it’s a classic story of how many people get addicted to opioids. We both suffered from chronic pain. Mine was in my neck and his was in his back,” 45-year-old Ms Ross said.
Before the trial started one of the Floyd family's lawyers said "the whole world is watching" the case.
The trial is expected to last about four weeks at the courthouse in downtown Minneapolis, which has been fortified with concrete barriers, fencing, and barbed wire.