Factual error: Once the cop sees Mercedes' body in the trunk, Les and his friends would likely be charged with kidnapping, which is a felony. Les and his friends would then be charged as adults.
Suggested correction: Les and friends had no criminal intent to engage in kidnapping, which typically involves demanding a ransom, which they also were not seeking. As odd as it was, Mercedes was put in the trunk, at least in part, for her own safety/protection. Even a charge of false imprisonment or unlawful restraint would not be likely to result in any conviction (or adjudication in juvenile court) because Les and his friends lacked the necessary mens rea or guilty mind. They might be "in need of supervision."