No. In some cases, they do, but in a large amount of cases they absolutely do not. It really depends upon the type of crime that was committed. If a felony is committed, and the officer has probable cause to believe that the person they are investigating has committed the crime, they can execute that arrest. Misdemeanors: if an officer is going to arrest someone for a misdemeanor like a theft charge or something like that, they can (in certain limited circumstances) arrest even if it didn’t occur in their presence. There are certain crimes like batteries and domestic batteries, that the officers don’t need to see. But there are a lot of other misdemeanors that if the officer didn’t see it, he can’t arrest the person. He has to do a report and provide information to the State’s Attorney’s Office to make a decision whether or not to file charges.