Quickly trying to educate myself on DNA and seminal fluids, etc. From this site, I'm learning that seminal fluid can be detected by the Brentamine test revealing acid phospatase (high levels indicate semen) and also the glycoprotein, p30 (also known as prostate specific antigen or PSA) which is not produce by females, but found in male urine, semen and blood. This antigen is present in semen, regardless of whether the male has had a vasectomy. So, semen can be detected, but who left the semen can be in question, depending on whether sperm can be found and analyzed (didn't Remy have a vasectomy?), or if the male sample is the same blood type as the female, etc.
http://what-when-how.com/forensic-sciences/sexual-assault-and-semen-persistence/