Would you step in, try to stop the offender and make a citizen's arrest? \"The types of offenses which warrant a citizen's arrest and those which do not are sometimes hard to distinguish. While citizen's arrest often was and still is a spontaneous phenomenon, at times it's also been an act performed by organized groups. \"From a legal perspective, from a pure cost-benefit perspective, there are probably few instances where a citizen's arrest makes sense. If you have to wait a few days for a marshal to come to town, then a citizen's arrest is probably more appealing.\"