The opening week of the trial of former Minneapolis police officer Derek Chauvin, facing murder and manslaughter charges for the death of George Floyd, has featured dramatic and emotional testimony.

Among those taking the stand in the heavily-guarded downtown Minneapolis courtroom have been Floyd's girlfriend, witnesses to his May 25, 2020 arrest and fellow police officers.

Chauvin, who is white, was seen on video kneeling for more than nine minutes on the neck of Floyd, a 46-year-old Black man who was being detained for using a fake $20 bill in a nearby store.

Here are some of the emotional comments made by witnesses during the first week of the trial.

Darnella Frazier

Frazier, an 18-year-old African-American woman, was walking to the convenience store, Cup Foods, with her eight-year-old cousin when she saw Floyd being arrested.

She began recording and it was her smartphone video that went viral and sparked protests against racial injustice and police brutality across the United States and around the world.

"It wasn't right. He was suffering. He was in pain," Frazier told the nine-woman, five-man jury hearing the case. "I knew it was wrong.

"It's been nights I stayed up apologizing and apologizing to George Floyd for not doing more and not physically interacting and not saving his life," she said.

Christopher Martin

Martin, a 19-year-old cashier at Cup Foods, sold the pack of cigarettes that Floyd paid for with a fake $20 bill.

Martin said he knew at the time that the banknote was counterfeit. "If I would have just not taken the bill, this could have been avoided," he said.

Floyd appeared to be "high" while in the store but "he seemed to be having an average Memorial Day, just living his life," Martin said.

Martin said he felt "disbelief and guilt" after learning Floyd had died.

Courteney Ross

Ross, 45, was Floyd's girlfriend of nearly three years.

She said they met at a Minneapolis homeless shelter where Floyd worked as a security guard.

She had gone there to visit the father of one of her sons, Ross said, and Floyd saw her looking sad in the lobby and asked if he could "pray" with her.

"It was so sweet," she said. "I had lost a lot of faith in God."

Ross acknowledged that both she and Floyd had struggled with opioid addiction.

"We both suffered from chronic pain," she said. "Mine was in my neck and his was in his back."

"We got addicted and tried really hard to break that addiction, many times."

Lieutenant Richard Zimmerman

Zimmerman, the longest-serving officer in the Minnesota Police Department, said Chauvin's use of force against Floyd was "totally unnecessary" and violated department policies.

"Pulling him down to the ground facedown and putting your knee on a neck for that amount of time, it's just uncalled for," he said.

Zimmerman said he had reviewed bystander video and police bodycam footage and he "saw no reason why the officers felt they were in danger."

"Once a person is cuffed, the threat level goes down, all the way," he said. "They're cuffed. How can they really hurt you?"

Donald Williams

Williams, 33, was among the crowd of bystanders urging the officers holding Floyd down to get off of him.

"You could see that he was trying to gasp for air, trying to breathe," Williams said. "You could see his eyes slowly rolling back in his head."

Williams, a mixed martial arts instructor, said Floyd was being held by Chauvin in a "blood choke" and he saw him lose consciousness.

Williams made an emergency 911 call after Floyd was taken away by ambulance.

"Murderers, bro... they just killed that man in front of the store," he told the 911 operator.

Derek Smith

Smith, a paramedic, said Chauvin still had his knee on Floyd's neck when he arrived but he believed Floyd was already dead.

He checked the carotid artery in Floyd's neck to see if he had a pulse. "I did not feel one," Smith said. "In lay terms, I thought he was dead."

Smith said he and his partner attempted to revive Floyd in the ambulance but their efforts were unsuccessful.

"He's a human being and I was trying to give him a second chance at life," he said.