U.S. District Court for the District of Arizona rulings
The federal trial court for Arizona. Its decisions are not binding on other courts but are often cited, especially in civil-rights cases about police conduct. Plain-English summaries from Criminal Defense Resources™; general education, not legal advice.
2 rulings, newest first.
Krause v. County of Mohave
In a civil lawsuit over a deputy's fatal shooting, a federal trial court in Arizona limited the plaintiff's police-practices expert. He could not offer legal conclusions, such as that the force was "not objectively reasonable" or that elements of a legal claim were met. He could not give ballistics or bullet-trajectory opinions, because his police, firearms, and gunsmith experience did not qualify him in that technical field, and he could not testify about medical matters. A new opinion he first gave at his deposition, months after the disclosure deadline, was excluded as untimely. The court found him qualified as a police-practices and use-of-force expert and allowed his testimony on whether deputies violated sheriff's office policies and accepted police practices, short of legal conclusions.
Rascon v. Brookins
In a civil lawsuit against Phoenix police officers over a man's death, a federal trial court in Arizona limited the plaintiffs' police expert, Roger Clark, to law enforcement use of force, training, procedures, and administration. He could not give medical opinions, including on cause of death or the physiological effects of a TASER, which the plaintiffs conceded he was not qualified to give. He could testify about whether the force, including the TASER, was justified and that officers should have acted differently, but could not say the officers acted unconstitutionally or used excessive force, because those are legal conclusions. The same order limited or excluded several other experts.