The fallacy of the two-minute acid phosphatase cut off

Research was carried out to determine whether the likelihood of obtaining a positive Acid Phosphatase (AP) test result is affected by the make and type of paper used. Also, we aimed to investigate the frequency of AP positive reactions occurring after 2min using a series of known semen dilutions and to determine whether spermatozoa transfer onto the paper during the act of AP screening. In this research, most brands of paper tested were able to detect a 1 in 40 semen dilution within 2min. Leaving AP test papers for longer will allow the detection of greater dilutions of semen and as the amount of ejaculation is not reliably known in most casework situations and levels of AP activity can vary in different men, this will increase the seminal detection rate in sexual offence allegations.