In Florida, a person does not commit a crime by being present when someone else commits the crime and knowing the crime was committed. However, a person can be guilty of a crime if he/she did not actually commit the crime but assisted the perpetrator during or after the crime. That is called being an accessory to the crime and can result in serious felony penalties.
For instance, if two people go to a park and Person A robs the victim. Person B is there when the robbery took place and ran with Person A after the robbery. That alone does not make Person B guilty of robbery or accessory to robbery. If the state cannot prove that Person B knew Person A was going to commit the robbery, Person B had no involvement in facilitating the robbery and Peron B did nothing to help Person A escape from the robbery, Person B would not be guilty of a crime. Of course, the state might still charge Person B for the crime and it may ultimately come down to what the jury believes, but mere presence at a crime is not sufficient to prove commission of the crime.
Add one more fact, and Person B would be guilty of a crime. Assume Person A planned to commit the robbery without Person B’s prior knowledge, Person B sees it happen and after the robbery both Person A and Person B run away. They both run to a car, and Person B drives Person A away from the scene of the robbery. This now becomes a situation where Peron B helps Person A get away from the scene of the crime knowing a crime was committed. Now, Person B would be guilty of accessory after the fact of the robbery. If Person A and Person B ran away separately and went to different destinations, Person B would not be accessory. But if Person B assisted Person A in any way to escape the crime, Person B would then be guilty of a crime him/herself.