9th Cir.

Diamond v. Collinson, et al.

June 22, 2026 ·3:22-cv-00346-SI ·Unpublished · By Aisha Johnson

The Ninth Circuit reversed a district court ruling that denied qualified immunity to two law enforcement officers involved in a fatal welfare check. The appellate court held that the law was not clearly established at the time regarding the use of less-lethal force against an armed, suicidal individual.

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Background

Douglas Diamond was shot and killed during a welfare check by Clackamas County and City of Sandy law enforcement officers. Diamond’s estate sued the City of Sandy, Clackamas County, and officers Michael Boyes, William Wetherbee, and Sergeant Sean Collinson, alleging violations of the Fourth and Fourteenth Amendments. The district court denied qualified immunity, finding triable issues of fact regarding excessive force and holding Sergeant Collinson liable under the integral participant doctrine.

The court’s reasoning

The Ninth Circuit reviewed the qualified immunity decision de novo but limited its scope to the second prong of the analysis: whether the law was clearly established. The court found no precedent placing officers on notice that using less-lethal force to disarm an irrational, suicidal individual with a loaded handgun in his pocket violated the Fourth Amendment. The court distinguished this case from prior excessive force precedents where suspects were unarmed, compliant, or posed no immediate threat. Regarding the integral participant doctrine, the court found no evidence that Sergeant Collinson agreed to a common plan involving unconstitutional conduct or acquiesced in it, as the officers reasonably treated the situation as a dangerous encounter.

What it means going forward

The case is remanded to the district court to proceed on excessive force, failure to train, and state law claims against the City of Sandy, County of Clackamas, and Officer Boyes, while the qualified immunity claims against Officers Wetherbee and Collinson are dismissed.