David Cornelius Smith lay face-down on the floor of the downtown Minneapolis YMCA, groaning, as a city police officer knelt on his back and another officer straddled his legs.

A video camera worn by one of the officers captured the Sept. 9, 2010, confrontation, which occurred after the YMCA asked police to eject Smith, a mentally ill 28-year old who was acting bizarrely. The video shows the officers used a Taser several times before they could subdue Smith. But after nearly four minutes holding Smith down, the officers realized he was not breathing. He died a week later.

Police Chief Tim Dolan has defended the actions of Officers Timothy Gorman and Timothy Callahan, saying "a tragedy can ensue" even when officers "act appropriately." The officers' attorney, Fred Bruno, noted that a Hennepin County grand jury cleared Gorman and Callahan of any criminal wrongdoing, and said that Smith has only himself to blame for his death, because he was "out of control."

But a lawsuit filed by Smith's uncle claims Gorman and Callahan suffocated Smith by putting excessive weight on his upper back, and cites the autopsy report that classifies the death as a homicide. By focusing on the officers' use of prone restraint, the suit calls into question a police practice that has raised concerns across the country. Bruno says prone restraint wasn't raised in the police internal investigation.

Medical experts who have studied the issue disagree about the danger of prone restraint. Still, officers are often warned in training programs about the potential harm to those being restrained, especially if the pressure on the back is prolonged. Minneapolis Police Department policy specifies that "when ANY restraint technique is used on a subject, the subject shall not be left in a prone position and shall be placed on their side as soon as they are secured."

Larry Smith, David Smith's uncle and a criminal defense lawyer in Chicago, considers the death of his nephew an "improper use of deadly force by police." "I am really shocked that the officers involved have not been prosecuted," he said.

A troubled life

David Smith's fatal encounter with Minneapolis police followed years of struggling with bipolar disorder and substance abuse, according to family members and a state report. Smith grew up in Peoria, Ill., and moved a few years ago to the Twin Cities to be in the Job Corps and then stayed, said his sister, Angela Smith.

A few weeks before he died, Smith visited his sister in Atlanta. "We talked about him getting readmitted for school," his sister said. "He was going to do some online classes."

Yet Smith was in a state of crisis. He had been hospitalized twice that year for psychosis, and the week before he died he went to a Twin Cities emergency room after overdosing on cold tablets, according to a report in October by Jo Zillhardt, a medical review coordinator with the state ombudsman for mental health and development disabilities.

A social worker placed him in a crisis residence, but he was discharged after two days when he left without permission. Zillhardt's report said there is no indication Smith was given medications at the residence.

Smith returned to a homeless shelter and a few days later turned up at the YMCA, where he was a member. He was walking around without his shirt, mumbling. He threw a basketball into a girls' kickball class and scared a 13-year-old boy in the YMCA's sixth floor gymnasium. A Y staffer called 911 at 3:45 p.m.

Within minutes, Callahan and Gorman arrived, but they were unable to persuade Smith to leave. They suspected he was mentally ill or affected by drugs or alcohol, they told a police internal affairs investigator. Smith resisted and punched Callahan in the jaw. The officers decided to use the Taser on him, though Callahan is heard on the video saying, "I've never done it before."

Once he realized Smith had no pulse, Callahan began giving Smith CPR. After paramedics arrived to take over the resuscitation, Callahan can be heard on the video calling his wife and saying. "I think me and Jimmy killed a guy."

Although paramedics restarted Smith's heart, he remained in a coma and died a week later. The Hennepin County Medical Examiner attributed Smith's death to "mechanical asphyxia," noting significant conditions that included the prone restraint position, cold medicines in his system, mental illness and physical exertion during the struggle.

Neither officer was disciplined, according to department spokesman William Palmer.

The lawsuit, filed in October, is being brought by Minneapolis lawyer Robert Bennett, who has won sizable damage awards in excessive force cases against the Minneapolis police. City officials declined to discuss the case because of the litigation.

Medical and police experts who reviewed the videos and autopsy report at the request of the Star Tribune differed on their interpretations.

Dr. Donald Reay, retired chief medical examiner for King County, Wash., said it was "a judgment call" to blame Smith's death on asphyxia, something he is not sure he'd have concluded. He said the report mentions other potential factors in Smith's death, including a "moderately abnormal" blood vessel.

Reay also noted studies by two San Diego researchers, Dr. Ted Chan and Dr. Tom Neuman, who concluded prone restraint does not cause death by showing that placing weights on the backs of individuals could not cut off their breathing.

Dr. Werner Spitz, a professor at Wayne State University, who said he has evaluated 75 to 100 cases of prone restraint, dismisses Chan's findings, saying they are done in laboratories and do not reflect what goes on in the streets.

Unable to breathe, Spitz said, Smith was afraid of "impending doom," which increased his heart beat. With carbon monoxide buildup inside his lungs and inability to take in oxygen, Smith developed acidosis "that brings on a haywire rhythm of the heartbeat." The heart abnormality may have contributed to Smith's death, Spitz said, but he was living with it before and "it does not exculpate the police from suffocating him."

George Kirkham, professor emeritus at Florida State University in the College of Criminology and Criminal Justice, said the officers "engaged in precipitous and premature physical involvement rather than talk to the guy from a distance." They used the Taser on him too many times, Kirkham said, then kneeled on his back "in a classic recipe for positional asphyxia."

John Peters, president of the Institute of Custody Deaths in Henderson, Nev., which trains police officers, said the officers had to be concerned for their own safety as well as the danger that Smith might hurt someone else.

He notes that the videos do not portray all the activity. "If the video shows that they had both knees on his back, and did not let him up until he became quiet, that would be outside the scope of best practice as we know it today," Peters said.

"It's a tragedy for everybody. The decedent, the decedent's family, the officers, the community."

Staff researcher John Wareham contributed to this article.

Randy Furst • 612-673-4224