When Nikita comes out of the bathroom, her feet are wet. The camera follows her down the hall where there is already a trail of wet footprints from a previous filming attempt.
Nikita tells her foster father, "I had just turned 18, so they were able to charge me with Murder 1." It is possible in every state in the United States to charge at least some juveniles with first degree murder, and especially possible to do so for a cop killer. What is actually impossible under 18, on the grounds of unconstitutionality, is sentencing a juvenile to death.