The 4th Amendment can only be violated by pubicly paid police, private individuals acting at the direction of public police, or privately paid police who have been deputized with the power to make arrests.
A search incident to a lawful arrest in a car can include the passenger compartment of a car if the arrestee is unsecured and can still access the interior of the car or if the police reasonably believes that evidence of the offense for which the individual was arrested for may be found in the car.
Police can search any area inside a car which could reasonably contain an item of evidence they had probable cause to look for.
Miranda warnings are required under the 5th Amendment if the individual is held in custody (such that they reasonably believe that they are not free to leave) and are interrogated by police in a way that might elicit an incriminating response.
Retrial is permitted where