Updated April 1, 2021 at 1:54 PM ET

Prosecutors began the fourth day of former Minneapolis police officer Derek Chauvin's trial on murder charges by calling George Floyd's girlfriend, Courteney Ross, to the stand. Ross spoke about her affection for Floyd; she also acknowledged that both she and Floyd struggled with opioid addiction.

In her emotional testimony, Ross described to the jury the man she knew, adding detail to a life that ended when Floyd died in police custody last Memorial Day.

Ross, 45, often smiled as she spoke about Floyd. But at times, she also needed to take moments to collect herself, growing emotional after she was asked to tell the story of how they met, for instance.

Ross said she met Floyd in August 2017 while waiting in the lobby of the Salvation Army's Harbor Light shelter in Minneapolis.

She was tired and frustrated, Ross recalled, as she waited for the father of her son to come down. She then heard a deep voice, asking her if she was OK. Ross said that she was not.

"He said, 'Well, can I pray with you?' " she recalled, weeping at the memory.

Floyd was working at the shelter as a security guard, she said.

After Ross told Floyd that she and her son's father were no longer in a relationship, he got her number – and over the next three years, they saw each other nearly every day, she told Minnesota Assistant Attorney General Matthew Frank.

Describing how the couple often went out for walks and to eat at restaurants, Ross said, "It was fun, it was an adventure, always, with him."

In the months before his death, Floyd was the head of security at Concha, a bistro and nightclub, Ross said. But he lost that job due to the COVID-19 pandemic, she added.

Ross described Floyd as "a mama's boy" — and she said he was hit hard by his mother's death in May 2018.

"When he came back from Houston, he seemed kind of like a shell of himself," she said. It seemed like he was broken and sad, she added.

"He was devastated," Ross said.

As Ross wept, Frank asked if she wanted to take a break.

"I'm OK," she said. "I can do it."

Ross also said that she and Floyd "both suffered with opioid addiction," acknowledging that drug use was a part of their relationship. She said both had gotten prescriptions for chronic pain — for her, in her neck, and for him, in his back, she said.

Despite repeated attempts to break free from addiction, she said, they struggled with opioids "every day." But there were stretches of time, she added, in which neither one was using the drugs.

In early 2020, both Ross and Floyd quit using drugs for "a long period," she said. But she said that by May, she suspected that Floyd had started using opioids again, adding that she also did so at least once that month.

The couple did not live together. At the time of Floyd's death, he was staying in an apartment with two roommates, Ross said.

When asked about the last time she spoke with Floyd, Ross said they talked by phone on the Sunday before he died.

In that conversation, Floyd said he was going to stay at the home of a friend named Sylvia whom he knew from the Salvation Army, Ross said. She said that Floyd seemed lonely and wanted to see a group of friends, including many who had lost their jobs. They were "just kind of being a family," Ross said.

She described Floyd as "very active," saying he loved sports and lifted weights every day as part of his workout.

"He was the type of person that would just run to the store," she said with a laugh.

Ross said she had never heard Floyd complain of shortness of breath – an observation that could play into how Floyd's health is perceived. Chauvin's defense team says that Floyd's physical condition, specifically problems with his heart, contributed to his death.

After the prosecution's initial round of questioning, Chauvin's attorney, Eric Nelson, asked Ross detailed questions about how she and Floyd acquired their opioids.

"Was Morries Hall the person that you and Mr. Floyd bought controlled substances from?" Nelson asked.

"We had," Ross replied.

Hall is the man who has been identified as Floyd's friend, who was in the passenger seat of the SUV Floyd drove to Cup Foods on the day he died. Notably, Hall's attorney filed court papers Wednesday, saying that Hall would invoke his Fifth Amendment right against self-incrimination and asking the court to quash a subpoena for him to testify.

That notice came hours after a Cup Foods clerk testified that Hall had tried to pass a similar $20 bill to the one Floyd used, but the bill was rejected because it seemed to be counterfeit.

In court, Nelson showed Ross a photograph – Defense Exhibit 1006, he said – that Ross identified as Hall. It was taken on May 25, 2020, showing Hall wearing red and white clothing.

Nelson then turned to an incident in early March 2020 when Floyd needed to be hospitalized.

Describing what happened, Ross said she was going to drive Floyd to work, but he wasn't feeling well.

"He was doubled over in pain" and said he need to go to the hospital, she said, so they went to an emergency room.

Ross said that she later learned the incident was due to an overdose. Floyd spent several days in the hospital, she said. Ross said she didn't know what drug had caused the overdose.

"You did not know that he had taken heroin?" Nelson asked.

"No," Ross replied, shaking her head.

Nelson then asked Ross to describe some pills she and Floyd acquired in March 2020. They weren't uniform in their size, she said. And under questioning, she said that their effect was different from opioids she had taken.

Describing opioids' usual effect of relieving pain and relaxing her, Ross said that the drug in the pills "seemed like it was a really strong stimulant" that kept her from sleeping and made her jittery.

She later testified that the couple got similar pills again in May, including a purchase a week before Floyd's death. Ross told Nelson that she believed those pills came from Hall, although she didn't see them being bought.

The Hennepin County medical examiner's autopsy report of Floyd's death ruled that it was a homicide, saying his heart and lungs stopped functioning "while being restrained" by police officers. But it also noted "other significant conditions," including fentanyl intoxication and recent methamphetamine use as well as heart disease.

The pills the couple took in March did not come from Hall, Ross said in response to Nelson's question.

Nelson later asked Ross about how much time Floyd spent with Hall – and whether she liked Hall.

"I didn't like Morries very much, no," Ross said, adding later that she "speculated" that Floyd would buy drugs from Hall.

Nelson then asked a series of questions that seemed to drive toward naming the people who supplied drugs to Floyd.

Ross said she was speculating when she told the FBI that Floyd's overdose in early March was due to heroin. She said she was also speculating when she told agents about whom she blamed for providing the drug.

Nelson asked, "Was that Shawanda Hill?" and Ross replied, "Yes."

Hill has been identified as the woman who was sitting in the back seat of the car with Floyd and Hall outside Cup Foods, according to police body camera footage from the scene.

Hill is expected to be called to testify later in the trial.

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