The Kastle–Meyer test is a presumptive blood test that justifies the presumption of the presence of blood. In this test, the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. The Rapid Stain Identification of Human Blood (RSID Hb) test is the confirmatory test that verifies the presence of blood in a fast, easy, and reliable manner. Positive results in these tests confirm the possibility of violence taking place, which resulted in the presence of bloodstains.
Identifying sperm cells on provided evidence is necessary to verify the allegation of sexual assault and provide the logical justification for processing the sample through differential extraction. The acid phosphate test is a presumptive test that helps identify seminal stains in rape cases. Spermatozoa visualization via staining is the confirmatory process for the identification of semen. It is done via Kernechtrot Picroindigocarmine Stain (KPIC), also known as the Christmas tree stain test. Positive results in these tests verify the occurrence of sexual assaults.
Forensic processing of sexual assault evidence is to identify the male perpetrator by DNA profiling. After the tests mentioned above, it is possible to conduct DNA sample amplification via Polymerase chain reaction and create a Short Tandem Repeats profile to identify the perpetrator. Typically, the total genotype frequency is greater when fewer than 13 STR loci are investigated, increasing the likelihood of a random match.
It is possible to observe that the blood sample and non-sperm fractions of DNA completely match the victim and cannot be connected to the suspect. At the same time, there is only a partial match of the sperm and male suspect on all loci except for TPOX. Consequently, it is difficult to use the provided results for conclusive evidence. A partial match may point to the presence of an additional perpetrator or genetic relatedness to the suspect.