THE PHYSICAL INGREDIENTS that made up James Chasse Jr.'s death on a Sunday afternoon in autumn are both well known and awful.

The police officers chasing an obviously terrified and mentally ill man. The tackle so forceful, witnesses could hear the "slap of bodies" bounce from Pearl District buildings. The kicks and punches and Taser strikes. The 16 broken ribs and the blood.

The indelicate handling of a mortally injured man, hogtied and hauled into jail like some kind of moaning deer carcass. The highway trip to a far-away hospital that never reached its destination.

But these have always been mere pieces of a tragedy that has haunted Portland and its police force ever since Chasse took his last breath in that patrol car in September 2006—and hardly the most outrageous. Because none of it gets to the lies about drugs, the ambulance ride that was waved off, the laughter, the lack of accountability. The things that really killed the 42-year-old, his family's lawyers say.

That stuff would have come out in court, if the city didn't agree to pay a record $1.6 million to Chasse's family. It hit a few news organizations in October 2010, but the complete story has mostly been hidden away in vast legal vaults. Until now.

Alien Boy: The Life and Death of James Chasse, a documentary and labor of love years in the making, will open this month at the Portland International Film Festival. From there, it will head to national festivals.

"Everybody knows about the story here [in Portland]. But what does it mean to Phoenix and Philadelphia?" asks Jason Renaud of the Mental Health Association of Portland, a producer of the film and friend of Alien Boy's director, Brian Lindstrom. (Former Mercury News Editor Matt Davis is credited as the film's writer.)

Of course, it's arguable that even people in Portland know what really happened. And why even a federal investigation that rapped the Portland Police Bureau for using an unconstitutional level of force against the mentally ill may not prevent it from happening again. Alien Boy wraps up that harsh truth in a 90-minute bow—drawing on little-seen, and some previously unseen, records and materials.

In depositions and in other testimony, Officer Christopher Humphreys—now sheriff of Wheeler County—numbly and carefully explains that he did a two-arm takedown of Chasse. Meanwhile, in footage captured while Chasse was at the county jail, Humphreys brags, to laughing guards, that he tackled Chasse. Humphreys also claimed Chasse was urinating on a building. He was not.

Witnesses—including Bret Burton, a then-Multnomah County sheriff's deputy partnered with Humphreys—wondered why bread crumbs in a baggy in Chasse's pocket were suddenly being called crack/cocaine. One cop, Officer Michael Bledsoe, lied to a witness that Chasse had 14 prior drug convictions. He had none.

Chasse can be heard pleading for a paramedic to "please don't go," but Sergeant Kyle Nice waves the ambulance away. Paramedics remembered being told about drugs, but were never told Chasse had been tackled, Tasered, and struck, or that he'd stopped breathing at one point while crumpled on the sidewalk—about the same time officers were milling about, blithely sipping on Starbucks. The state medical examiner said Chasse likely would have lived with prompt medical attention.

The investigation into Chasse's death sprawled for years. Nice and Humphreys were eventually punished in connection with Chasse's death, but not until 2009—and then were given only two-week suspensions, for failing to secure medical care.

Allegations of untruthfulness were never seriously probed. Same for the kicks and punches. A training division analysis, conducted not long after the death, found the initial police chase outside of training policy. But the report was sealed until the settlement in 2010 and internally disputed.

Former Portland Police Association President Scott Westerman—later fired from the bureau for untruthfulness—stars prominently as a reminder that union politics remain a strong deterrent to accountability. When Humphreys was taken off active duty in another case years later, after he fired a beanbag shotgun at a 12-year-old girl, Westerman led 600 union members in a march on city hall.

After Chasse's death, Portland police officers were all given extra training to help them better identify and respond to people in crisis. Federal reforms are supposed to further help the bureau refine how it reacts to those perceived to be ill. But the film plainly shows that the officers who chased Chasse recognized he was mentally ill and went after him all the same.

"Seeing mental illness won't save someone," says Tom Steenson, the attorney hired by Chasse's family. "Don't smash and beat someone and cover it up."

Alien Boy also reminds us of the "Jim-Jim" his loved ones lost and regained, and then lost again.

Friends and ex-lovers tell us all about the talented and androgynous artist and writer and musician whose youthful exuberance crumbled under the weight of schizophrenia that left him an ill runaway. The film draws its title from a song written about Chasse. He resurfaced as a young man, enjoying a quiet life of coffee and books and meals with his mother, but had drifted again, going off his medication, when he was killed.

Why did he run that day? His past was prologue.

At age 19, he was beaten by officers in Utah and wound up in a psychiatric hospital.

Two days before he died, Ela Howard, a Project Respond worker, came to the door of his fetid room and persuaded him to come outside. He did, but saw the cop she brought and ran. The fear had never left him. The officer wanted to chase him then, but Howard kept him back. She also begged him to flag Chasse as someone ill and in need of Project Respond. That never happened.

On Monday, February 4, Renaud screened Alien Boy for Police Chief Mike Reese and other senior staffers, as well as Mayor Charlie Hales' chief of staff, Gail Shibley, and Hales' public safety director, Baruti Artharee. Asked about their responses, neither office replied with substantial comments in time for the Mercury's deadline.

But the smiling brusqueness of Humphreys during the depositions says more than enough.

Asked if he'd do the same thing again, he pauses and then gestures toward the attorneys: "Assuming none of this would happen? Yes."