Federal Rules of Criminal Procedure - Rule 51. Preserving Claimed Error
(a) Exceptions Unnecessary.
Exceptions to rulings or orders of the court are unnecessary.
(b) Preserving a Claim of Error.
A party may preserve a claim of error by informing the court -- when the court ruling or order is made or sought -- of the action the party wishes the court to take, or the party's objection to the court's action and the grounds for that objection. If a party does not have an opportunity to object to a ruling or order, the absence of an objection does not later prejudice that party. A ruling or order that admits or excludes evidence is governed by Federal Rule of Evidence 103.