Say a police officer is undercover (we'll stick to America). They are trying to find evidence of someone committing a crime? However, the person unknowingly admits to the officer that they plan to commit a less serious crime, (for example the police could be bust a drug smuggling operation, but the person has punched someone in the face).

Is the police officer legally obligated to report the crime or are they allowed to continue on until they have found the evidence they need to prosecute for the larger crime?

  • 1
    If movies taught me anything, the answer is no.
    – MWB
    Nov 6, 2020 at 18:19

3 Answers 3


Police have discretion in the enforcement of the law

Which is to say, police get to decide which crimes they make arrests for, which they handle with warnings, which they report and which they ignore. This applies whether they are in uniform, undercover or off-duty.

If they abuse this discretion then they are liable to disciplinary action. If they apply it corruptly or otherwise illegally then they are liable to criminal sanction.


The answer to your question is the Mathmatician's Yes. They are legally obligated to report it (normally to their handlers after the fact in a timely manner) and they are allowed to continue searching for evidence for the larger crime. It's just one more list to charge the guy with when the government agency decides to move on the "target". The continuation of the investigation would hinge on how likely they can gather evidence on the guy from the initial complaint. Punching buy who is in debt in the face is different from punching a random guy in a sports bar over cheering the opposing team's victory.

What's more, undercover police may even have some authorization to participate in a crime in order to maintain cover!

Per FBI guidelines according to this article here, undercover agents are not allowed to commit any federal, state, or local crimes unless authorized by superiors. This often contains a list of specific crimes such as purchasing or selling of drugs (to establish a rapport with a targeted dealer) as well as a generalized "unforseen crimes" (i.e. technically, they can't Jwalk or speed. But if the target wants you to walk and talk with him as he illegally crosses the street OR wants you to do 75 in a 55, you can go ahead with that). And some aren't nearly as petty, though generally using physical force has to be very much justified and maintaining cover is never a defense to murder or other similar crimes. If the unforseen crime the agent participates in is over the top, they can share in the legal culpability.

Ultimately, the undercover and his superiors will make a determination of what charges will be brought against the target at anytime. The police do not have arrest and book a criminal for a known crime in an immediate manner, so long as they get it in before the statute of limitations is up on the incident. So if the target admits to punching a guy in the face to the undercover, the undercover should report it to his handlers, and they will determine if they need to execute the arrest or wait and continue on the investigation.

  • It is not correct that police must make an arrest for crimes that are observed. Nov 6, 2020 at 22:46
  • @GeorgeWhite: It depends on the Jurisdiction (Local, State, and Federal) in the U.S. A Federally run undercover op does not care about speeding because that's a local/state issue. Similarly Local/States don't have to care about the target being an illegal immigrant because immigration is strictly federal jurisdiction (Though they can and often do let the responsible jurisdiction know about it.). There is also prosecutorial discretion which allows them to not prosecute a crime for whatever reason. There is no obligation to report every crime.
    – hszmv
    Nov 9, 2020 at 14:21
  • Yes, but the discretion is much broader than that. I suggest googling "must arrest". Nov 11, 2020 at 2:28

No, while there are a limited number of jurisdictions that have "must arrest" laws for domestic violence, in general police in the U.S. have wide digression as to what crimes they witness will lead to an arrest.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .