Two paramedics have told a Minneapolis court that George Floyd had no pulse and did not appear to be breathing when they arrived at the scene.
Former police officer Derek Chauvin is accused of killing Floyd by kneeling on his neck for more than nine minutes during an arrest in May 2020.
Paramedic Seth Bravindar said he had to ask Chauvin to get off Floyd so that they could access the patient.
Earlier, the court heard emotional testimony from Floyd's girlfriend.
Courteney Ross described their first kiss, and their struggle with opioid addiction on the fourth day of Chauvin's trial.
Chauvin, 45, who was fired from the Minneapolis police force, denies charges of murder and manslaughter.
What was the paramedics' testimony?
Bravinder said the initial call-out was deemed non-life threatening although that soon changed.
He told the court he initially thought that a struggle was taking place when he and his partner arrived on the scene, but quickly realised that Floyd, 46, was limp.
Asked about video footage showing him gesturing to Chauvin, Bravinder said he wanted to "have him move" and this was "so we could move the patient".
His partner Derek Smith checked Floyd's neck for a pulse but could not find one. "In lay terms, I thought he was dead," Smith said.
"When I arrived on scene there was no medical services being provided to the patient," he added.
Bravinder cradled Floyd's head to prevent it from hitting the road as they transferred him to a stretcher.
They put him in an ambulance and started chest compressions.
At one point Smith thought he saw electrical activity from Floyd's heart and delivered an electrical shock to try to restart it. "He was a human being and I was trying to give him a second chance at life," he said.
Bravinder said he had to stop the ambulance en route to the hospital to help his colleague after the heart monitor showed Floyd had flatlined - his heart had stopped. All further efforts to resuscitate Floyd failed.
What did Floyd's girlfriend say?
Courteney Ross is the first person to testify who personally knew Floyd.
She told the court that she met him in 2017 in the lobby of a Salvation Army homeless shelter, where he worked as a security guard and she was waiting to see the father of her son. She said Floyd asked if she would pray with him.
"It was so sweet and at the time I had lost a lot of faith in God," she said, adding that they kissed that night.
She said their first meeting was "one of my favourite stories to tell".
Ross said they both suffered from chronic pain, and were addicted to opioids.
"Addiction, in my opinion, is a lifelong struggle," she said. "It's not something that comes and goes, it's something I'll deal with forever."
She did not specifically address whether Floyd was using opioids on the day he died.
A statement from Floyd family lawyers Ben Crump and Antonio Romanucci denounced "defence attempts to construct the narrative that George Floyd's cause of death was the Fentanyl in his system".
"We want to remind the world who witnessed his death on video that George was walking, talking, laughing, and breathing just fine before Derek Chauvin held his knee to George's neck, blocking his ability to breathe and extinguishing his life," it said.
What else has happened at the trial?
Jurors also heard from David Pleoger, the supervising police officer on duty that day, who said he only learned later in the evening that Chauvin had restrained Floyd by kneeling on his neck.
He told the court that an officer should stop using the knee as a restraint once "you get control of the situation" and the suspect is in handcuffs.
"Leave someone on their stomach for too long, their breathing will be compromised, so you'll want to get them up out of that position," he said.
Defence lawyer Eric Nelson sought to play down the significance of his testimony by saying Pleoger had "not reviewed the entirety of the evidence in this particular case".
The trial began on Monday with the Prosecutor Jerry Blackwell saying Chauvin had "betrayed his badge" and used "excessive and unreasonable force".
Defence lawyers have indicated they will argue that Floyd died of an overdose and poor health, and the force used was reasonable.
Footage from both witnesses' mobile phones and the police officers' bodycams have been shown at length. At one point, Floyd can be heard pleading with officers: "I'm not a bad guy", while the police officer is heard telling a bystander: "We had to control this guy because he's a sizeable guy. It looks like he's probably on something.
Several witnesses have also taken the stand, including four children who were under the age of 18 at the time of the arrest, and spoke of their trauma at what they saw.
Shop employee Christopher Martin - who inadvertently set off the tragic events after alerting his manger to a fake $20 bill Floyd had used to buy some cigarettes - has spoken of his "disbelief and guilt". "If I'd have just not taken the bill, this could have been avoided," he told the court.
Throughout the testimony, Chauvin has been taking almost constant notes. Three other officers charged with aiding and abetting second-degree murder will go on trial later in the year.
Why is this case so important?
The video footage of a white police officer kneeling for a prolonged period on the neck of an African-American caused outrage and led to global protests and a racial reckoning in the US.
Floyd's death had followed on the heels of several other high-profile cases of African-Americans dying at the hands of police officers.
Former President Barack Obama said the protests represented a "genuine and legitimate frustration over a decades-long failure to reform police practices and the broader criminal justice system".
African-Americans are disproportionately more likely to be fatally shot by police and arrested for drug abuse and five times more likely than white Americans to be imprisoned.
Police officers have rarely been convicted - if they are charged at all - for deaths that occur in custody, and the verdict in this trial is being widely seen as an indication of how the US legal system will treat such cases in future.