When police put up the take around a crime scene they are investigating it becomes a serious issue if you go past the police tape.
Now if you had a kid that ran into the police scene and you had to cross the police tape to go get your kid and then left the crime scene then you likely would not get into trouble.
But if you just intentionally cross the police tape and the police are present and investigating the scene then you can be arrested and be taken to jail.
You can be charged with interfering with law enforcement and serve a year or 2 in jail as a result of crossing that police tape.
So do not cross the police tape if you see the police tape up as it can get you arrested and into serious trouble.