For a normal random person, a grey man. In the real world, a single collision could be enough for the police to acquire further access to people they are already looking at. If the police want access to your phone for other reasons (drugs, taxes, illegal speech) they can use that one collision to get a warrant which will give them greater access.
It is akin to cops wanting to search a car. They don't need a warrant. They only need to follow the car until it breaks any number of traffic laws. Then the resulting traffic stops lets them talk to the driver, who seems evasive, which gives them probable cause, which gets them a warrant to perform a full search. The accidental collision, week evidence of an offending image on the phone, opens the door to whatever other investigation they want to do.
It is akin to cops wanting to search a car. They don't need a warrant. They only need to follow the car until it breaks any number of traffic laws. Then the resulting traffic stops lets them talk to the driver, who seems evasive, which gives them probable cause, which gets them a warrant to perform a full search. The accidental collision, week evidence of an offending image on the phone, opens the door to whatever other investigation they want to do.