The federal courts consistently hold that a law enforcement officer has a constitutional obligation to prevent a fellow officer from violating a citizen's constitutional rights when there is a reasonable opportunity to do so.1 The issue has arisen primarily in Fourth Amendment excessive force arrest cases.2 Whether an officer's use of force in making an arrest comports with the Fourth Amendment depends upon whether it was objectively reasonable.3 In O'Neil v. Krzeminski,4 the U.S. Court of Appeals for the Second Circuit reasoned that when there is an episode "of sufficient duration" that affords the "stand-by" officer a reasonable opportunity to prevent a fellow officer's infliction of excessive force, his failure to do so renders him a "tacit collaborator" in the unconstitutional conduct.
Whether an officer had sufficient time or capability to prevent the constitutional violation is normally an issue of fact for the jury.5 "In deciding whether an officer had a realistic opportunity to intervene, courts may consider, among other factors, the length of the excessive force, the number of blows involved, and the positions of the bystander officers relative to the altercation."6
