The different semen in case of gang rape is identified by:-
Single photon fluorimetry has been used to differentiate between different semen in a gang rape case TESTS FOR SEMINAL STAINS Creatine phosphokinase test Acid phosphatase testQ Florence testQ (Choline iodide crystals) Barberio's test (crystals of spermin picrate)
Acid phosphatase test
Christmas tree stain
PSA
Single photon flourimetry
Trace evidences