State v. Moore, 361 Or. 205

Background

Defendant (Moore) charged with murder and arson after a fatal garage fire; a co‑defendant (Richardson) pleaded guilty and agreed to testify for the state.
At trial the state called eight witnesses (including fire investigators and an eyewitness); during the state’s case the prosecutor disclosed a newly discovered insurance investigator (Gunsolly) who would say the fire was arson.
Defense moved to exclude the newly disclosed evidence but expressly opposed a mistrial, stating he wanted to proceed with the jury then seated.
The trial court admitted the insurance investigator’s anticipated testimony but then, sua sponte and over Moore’s objection, declared a mistrial after codefendant moved for one; the jury was discharged and Moore was reindicted.
Moore moved to dismiss on double/ former jeopardy grounds under Article I, §12 of the Oregon Constitution (and the Fifth Amendment); the trial court denied the motion, prompting Moore’s petition for mandamus to the Oregon Supreme Court.

Issues

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the trial court’s sua sponte mistrial over defendant’s objection met the “manifest necessity” standard under Article I, §12	The mistrial was a proper exercise of discretion to cure prejudice from admitting newly disclosed expert evidence; defendant’s objection was equivocal	The state failed to show manifest necessity; prosecutorial error caused the prejudice and defendant unequivocally objected and wished to proceed with the jury	The court held the state did not meet its burden; the mistrial violated Article I, §12 and reprosecution is barred
Whether prosecutorial mid‑trial discovery of a key witness justified reopening/ retrial	State argued fairness required allowing the new evidence and possibly retrial to protect public justice	Defense argued the state’s failure to identify the witness before trial was its mistake and cannot justify aborting a trial over defendant’s objection	The court treated the prosecutor’s lack of preparedness as significant weight against finding manifest necessity
Whether prior testimony (eight witnesses) made retrial unfairly prejudicial	State implied the trial court remedied prejudice by granting mistrial	Defense argued prior testimony gave prosecution an unfair preview and opportunity to prepare witnesses for retrial	The court found the prior testimony increased potential prejudice and weighed against permitting retrial
Whether mandamus relief is appropriate to prevent reprosecution	State contended ordinary remedies suffice; the trial court’s discretion should be respected	Defendant sought mandamus because retrial would irreparably violate his constitutional right	The court granted a peremptory writ of mandamus directing dismissal with prejudice

Key Cases Cited

United States v. Perez, 22 U.S. 579 (establishes "manifest necessity" doctrine for mistrials)
Arizona v. Washington, 434 U.S. 497 (requires a high degree of necessity and flexible, case‑specific inquiry)
Downum v. United States, 372 U.S. 734 (government unpreparedness to try key witness after impaneling jury disfavors retrial)
United States v. Jorn, 400 U.S. 470 (plurality: sua sponte mistrial without considering continuance can bar retrial)
Wade v. Hunter, 336 U.S. 684 (military‑tactical circumstances can justify reprosecution — distinguished as inapposite)
State v. Cole, 286 Or. 411 (Oregon case applying manifest necessity and distinguishing physical necessity from other necessities)