Utah Court of Appeals
Can defense counsel challenge curative instructions they helped craft? State v. Thornock Explained
Summary
Thornock was convicted of aggravated robbery of a Super 8 motel after his girlfriend testified that he stole duct tape and a mask from Walmart before the robbery, then burned evidence afterward. The court denied his motions to exclude his statement ‘I don’t steal, I kill’ and to disregard his girlfriend’s testimony as inherently improbable.
Practice Areas & Topics
Analysis
Background and Facts
In State v. Thornock, defendant Robert Thornock was convicted of aggravated robbery of a Super 8 motel. The case centered on testimony from Thornock’s then-girlfriend, who testified that Thornock stole duct tape and a hunting mask from Walmart before the robbery, then burned evidence afterward. During closing arguments, the prosecutor made statements suggesting that merely looking at or buying duct tape could implicate Thornock in the robbery, prompting defense counsel to object and request a curative instruction.
Key Legal Issues
The Utah Court of Appeals addressed four main issues: (1) whether the curative instruction adequately addressed prosecutorial misconduct; (2) whether the trial court properly admitted Thornock’s statement “I don’t steal, I kill” under Rule 403; (3) whether the girlfriend’s testimony was inherently improbable under State v. Robbins; and (4) whether the trial court properly applied collateral estoppel to bar Fourth Amendment arguments.
Court’s Analysis and Holding
The court applied the invited error doctrine to bar review of the curative instruction challenge. Because defense counsel not only approved the instruction but “actively participated in crafting it,” Thornock could not later claim it was insufficient. The court found the “I kill” statement was properly admitted as relevant to Thornock’s denial of stealing, and its prejudicial effect was mitigated by his immediate clarification. Regarding the girlfriend’s testimony, the court held that inconsistencies and motives to lie go to credibility, not inherent improbability, especially when corroborated by physical evidence.
Practice Implications
This decision reinforces that Utah courts strictly apply the invited error doctrine when counsel participates in crafting jury instructions. Practitioners must carefully consider whether to collaborate on curative instructions, as doing so may waive appellate review rights. The ruling also demonstrates that witness credibility challenges require more than showing inconsistencies or bias—corroborating physical evidence can defeat inherent improbability claims even when witness motivations are questionable.
Case Details
Case Name
State v. Thornock
Citation
2020 UT App 138
Court
Utah Court of Appeals
Case Number
No. 20180869-CA
Date Decided
October 8, 2020
Outcome
Affirmed
Holding
The trial court properly denied defendant’s evidentiary motions and directed verdict motion where defense counsel invited error regarding curative instruction, the challenged statement was relevant and not unfairly prejudicial, and witness testimony was corroborated by physical evidence.
Standard of Review
Invited error doctrine bars review when counsel affirmatively approves proceedings; abuse of discretion for rule 403 evidentiary rulings; clear error for trial court’s decision to decline disregarding witness testimony due to inherent improbability; plain error for Fourth Amendment arguments
Practice Tip
When objecting to prosecutorial statements, avoid participating in crafting curative instructions if you intend to preserve the issue for appeal, as active participation constitutes invited error.
Need Appellate Counsel?
Lotus Appellate Law handles appeals before the Utah Court of Appeals, Utah Supreme Court, California Court of Appeal, and the United States Court of Appeals for the Tenth Circuit.
Related Court Opinions
About these Decision Summaries
Lotus Appellate Law publishes these summaries to keep practitioners informed — not as legal advice. Each case turns on its own facts. If a decision here is relevant to your matter, we’re happy to discuss it.