Unless there is a good medical reason for a medical professional to perform any kind of search internally on a prisoner there is no need for a nurse to perform a cavity search. Cavity searches are done to ensure the safety of all involved at the prison. To check for contriband items such as weapons, drugs and many other things that you may not expect to find hidden inside a persons rectum. Generally a cavity search is not done without need because when an inmate is concealing something in their rectum, especially if it is a weapon or an amount of drugs such as cocaine, ice, speed etc (which they have sealed in a condom or other wrapping) they will be reluctant to do the squat and cough for risk of it coming out, or in the case of a weapon, especially a sharp one, the risk of severe injury and pain. Under no circumstances should you be required to do a cavity search, if however something goes wrong in removal of a sharp object then you may be required to step in and provide assistance.