Rick's prosthesis uses a suspension mechanism known as a shuttle lock. It requires a liner to be worn over the residual limb that is fitted with a steel pin on the end. The pin is inserted into the lock in the prosthesis and that holds it in place. Rick does not push the button on the prosthesis to release the pin when he doffs the prosthesis because he is not wearing the requisite liner with the steel pin. This would not be typical.
Jordan says the chain of evidence was broken once Paul treated Lorelei. In fact, there was a clear chain of evidence: he removed the tampon, he could testify as to who took it to the lab, then that person could testify it was taken to the lab, then the lab technician could testify as to the analysis. The police would get consent from the victim and seize the tampon as evidence and perform their own test on it. Due to the short period of time, no reasonable argument could be made as to how the suspect's semen was found- no one at the hospital could have tampered with the evidence to obtain the end result.