Time and again throughout the murder trial of Derek Chauvin, defense attorney Eric Nelson has found ways to bring up George Floyd’s drug use.

He has repeatedly highlighted the toxic mix of substances found in Floyd’s system, floated the possibility that Floyd may have ingested drugs rectally and asked expert witnesses whether the handcuffed man’s inability to breathe in his final moments may have resulted from an overdose.

As Nelson began his formal defense of the former Minneapolis police officer charged with Floyd’s killing, he sought to turn jurors’ attention to the deceased man’s drug addiction — a complex and delicate task that legal scholars say is fraught with risk, in part because Americans’ attitudes about drug use have shifted significantly in recent years.

Attempting to justify the officer’s use of deadly force as a legitimate response to an intoxicated and potentially dangerous suspect could instead be seen as an effort to demonize Floyd, whose death sparked a global reckoning over racial injustice, inequality and police brutality.

“We would be lying to ourselves if we didn’t point out that there’s a long history of making Black victims of police violence dangerous,” said Ekow Yankah, a criminal law professor at Cardozo School of Law at Yeshiva University. “And not just dangerous, but dangerous in a way that requires incredibly violent submission because of the shadow of drugs.”

During the trial, jurors have learned about Floyd’s opioid addiction, which he struggled with for at least four years, and about a May 2019 overdose of Percocet that required hospitalization.

After two weeks of the trial in which prosecutors used video evidence and witness testimony to make the case that Chauvin’s pressed knee on Floyd’s neck was the chief cause of his death, Nelson has prepared a collection of witnesses and evidence to make the case that Floyd’s abuse of fentanyl and other medical challenges led to his death, according to court filings. On Tuesday, Nelson called several witnesses who saw Floyd on the day of the May 2019 overdose.

While the strategy harks back to previous successful efforts to gain acquittal for defendants by highlighting a victim’s flaws, the trial has already showcased how much times and attitudes have changed, said Robert Bennett, a Minneapolis-based lawyer who has represented victims in police brutality cases.

When Floyd’s girlfriend, Courteney Ross, took the stand on April 1 and described their joint battles with opioid addiction, she was greeted with empathy from both the prosecution and defense attorneys.

“I’m sorry to hear about your struggles with opioid addiction,” Nelson said as he began his cross examination of Ross. “Thank you for sharing that with the jury.”

Ross was called as a witness by the prosecution, a move designed to humanize Floyd while dealing with the issue of his drug use in a sympathetic way, Bennett said.

Her treatment by the defense stood out as a departure from how witnesses with admitted drug use may have been treated in the past, said Yankah.

“A generation ago, the first thing people would have done was stand up and undermine her testimony,” casting her views aside as those of an untrustworthy drug addict, Yankah said. “Now, this defense can’t do that. They have to play this much more gently.”

That hasn’t stopped Nelson from repeatedly finding subtle ways to remind the jury of Floyd’s condition. After Floyd’s death in Minneapolis on May 25, 2020 — for which prosecutors have charged Chauvin with second- and third-degree murder and manslaughter — toxicology reports detected methamphetamine and fentanyl in the deceased man’s system.

“Are you familiar with the impact of taking certain narcotics inter-rectally, rectally?” Nelson asked Bradford Wankhede Langenfeld, the emergency room physician who pronounced Floyd dead, during testimony last week. “And that ultimately can provide a more powerful or rapid onset of an impact, right?”

Langenfeld responded in the affirmative. A few minutes later, prosecutor Jerry Blackwell asked Langenfeld if there was evidence that Floyd had ingested drugs in that way.

“I had no information to suggest that,” he said.

Nelson has contended that Floyd’s claim to officers that he “was just hooping earlier” was a slang term for a kind of drug ingestion. Prosecutors have asserted that Floyd was referring to playing basketball — the more conventional meaning of “hooping.”

And Nelson has used other words spoken by Floyd shortly before his death to draw attention back to the drugs that were in his system and suggest that Floyd had admitted to being high.

Using audio from police body cameras, Nelson asked two law enforcement witnesses on Wednesday whether they had heard Floyd say “I ate too many drugs” while officers were arresting him. Sgt. Jody Stiger of the Los Angeles Police Department, a paid witness for the state, said he could not make out what Floyd said, while James Reyerson, a special agent with the Minnesota Bureau of Criminal Apprehension, initially agreed with Nelson’s recitation of the hard-to-discern audio.

After the prosecution played a longer version of the clip, Reyerson clarified that he thought Floyd’s words sounded more like, “I ain’t do no drugs.”

Nelson has made two main arguments related to Floyd’s drug use — first, that opioids, rather than police force, killed Floyd; and second, that the 223-pound man was more of a threat to officers because he was under the influence.

Although the two arguments work in tandem, Bennett said that the second is an attempt to dehumanize Floyd and justify Chauvin’s decision to put his knee on the handcuffed man’s neck to prevent him from rising up and attacking at any moment.

Chauvin himself made that argument shortly after Floyd was taken away in an ambulance, according to body-camera footage played at the trial.

“We had to control this guy because he’s a sizable guy. It looks like he’s probably on something,” Chauvin was heard saying in a video.

At a deeper level, the repeated references to Floyd’s drug use play into a classic sentiment that because Floyd was an addict, jurors should think twice about sending a police officer to jail over his death, said Bennett.

“It’s the same sort of victim-blaming that has been used by defense attorneys for as long as I’ve been practicing, which is 45 years,” he said. “It’s not anything unexpected, imaginative, novel — it’s what they have to throw at the wall, so they’re throwing it.”

The defense team’s motion in August to dismiss the case laid out its argument in stark terms — one expected to be repeated during the trial this week and in closing arguments.

“Put simply, Mr. Floyd could not breathe because he had ingested a lethal dose of fentanyl and, possibly, a speedball. Combined with sickle cell trait, his pre-existing heart conditions, Mr. Floyd’s use of fentanyl and methamphetamine most likely killed him,” Chauvin’s lawyers wrote.

Prosecutors have taken the death-caused-by-drugs defense seriously, lining up more than a half-dozen medical witnesses to say repeatedly that Floyd was the victim of a homicide rather than an overdose.

Their most effective witness on that front may have been Martin Tobin, a Chicago-area pulmonologist and critical-care doctor who specializes in the science of breathing. In hours-long testimony Thursday, Tobin said in emphatic terms that Floyd died as a result of Chauvin’s force on his neck and back, and that his drug use and underlying medical conditions were not to blame.

“A healthy person subjected to what Mr. Floyd was subjected to would have died as a result,” Tobin told the jury.

Nelson pressed Tobin on Floyd’s drug use, particularly the combination of methamphetamines and fentanyl that he has repeatedly referred to as “speedballing.” Although Tobin acknowledged that such a combination could be deadly, his testimony was welcomed by Floyd’s family attorneys as pivotal.

“We’re so grateful that Dr. Tobin was so effective in presenting his testimony that completely destroyed the defense’s theory that George Floyd died as a result of trace amounts of drugs or a health condition,” Ben Crump, an attorney for Floyd’s family, said Friday on CNN’s “New Day.”

Nelson’s office declined to comment. His team has submitted a witness list with more than 15 medical professionals listed as “defense experts” to help build a case that Floyd’s health issues and drug use killed him.

Jon Zibbell, who studies illicit drug use and public health as a senior scientist at the think tank RTI International, said he agreed with the medical officials who disputed the overdose theory.

He said that swallowing fentanyl in pill form, as Floyd is alleged to have done, is unlikely to cause an overdose and that Floyd had probably built up a tolerance for the drug after years of use. People under the influence of opioids, he said, are generally “very relaxed and reasonable” and not prone to violence, he said, citing his own research.

Chauvin’s stated fear of Floyd may instead have reflected his own biases, Zibbell said.

“The use of drugs and the fear of people becoming violent has a long history in the United States to justify harsh policing and excessive force,” he said. “What the literature shows is that that has a lot more to do with the type of person than the type of drug.”

He cited the 1992 police beating of Black motorist Rodney King, which was captured on videotape. The four officers involved were acquitted, and one of them testified of fears that King was on PCP, a drug the officer contended gave King “hulk-like strength.” No PCP was found in King’s system.

In 2014, Ferguson, Mo., police officer Darren Wilson told a grand jury that he had shot and killed Michael Brown after the teenager displayed “Hulk Hogan”-like strength — adding, “It looks like a demon.” Brown had traces of marijuana in his system. Wilson was not indicted.

In 2016, the police officer who shot and killed Philando Castile shortly after pulling him over near Minneapolis claimed he had smelled marijuana in the vehicle.

“I thought if he has the guts and the audacity to smoke marijuana in front of the 5-year-old girl, and risk her lungs and risk her life by giving her secondhand smoke, and the front seat passenger doing the same thing, then what, what care does he give about me,” the officer, Jeronimo Yanez, told investigators.

He was acquitted on all charges.

Bennett said such overt attacks on deceased victims may be less effective in Chauvin’s case, especially because jurors have seen so much videotaped evidence of Floyd’s final minutes. He compared the case to that of another Minneapolis police officer, Mohamed Noor, who was convicted in 2019 of shooting and killing an unarmed woman who had called 911 for help. Bennett, who represented the woman’s family in a civil lawsuit, said jurors in the criminal case did not take it well when Noor’s defense attorneys referred to the victim as “the threat.”

“You could see the jurors cross their arms and look down and shake their head,” he said, noting that the jury in the Chauvin case was not being shown. “We don’t know what’s happening here in the same sort of direct observational way, but I can’t believe this is going over that great, given the video evidence that we’ve all seen.”

But Nelson’s task in the days ahead may simply be to create enough questions among jurors about Floyd’s drug use that they cannot all agree that Chauvin is guilty beyond all reasonable doubt, said Yankah.

“Defense lawyers only need one person with a conviction of reasonable doubt,” he said. “You need somebody who believes that there’s reasonable doubt to hold out — and it’s enough.”

Kim Bellware contributed to this report.