Yes, absolutely. An improper instruction to the court-martial panel on the legal elements of an offense is a very serious error that can invalidate a conviction on appeal. The military judge has a fundamental duty to accurately and completely instruct the panel members on the law they must apply to the facts of the case. These instructions are the legal roadmap that the jury uses to reach its verdict.
An improper instruction can take several forms. The judge might omit one of the essential elements of the offense, which would allow the panel to convict without finding that the government proved every part of its case. The judge might misstate an element, giving the panel an incorrect definition of the law. Or, the judge might refuse a defense request for an instruction on a relevant legal defense, such as self-defense or mistake of fact, that was reasonably raised by the evidence.
If a defense attorney believes the judge has given an improper instruction, they must make a formal objection on the record to preserve the issue for appeal. After a conviction, the appellate defense attorney will argue that the instructional error was so significant that it deprived their client of a fair trial. If the appellate court agrees that the error was substantial and that it could have reasonably affected the panel’s verdict, they will set aside the conviction and may order a new trial with proper legal instructions.