Comparative study of the sensitivity and specificity of the zinc and acid phosphatase spot tests for the detection of seminal stains

The sensitivity and specificity of a zinc spot test for the detection of semen were compared with those of an acid phosphatase detection method. As screening techniques both tests were found to be very sensitive, but the zinc test was more specific and was more reliable in older and especially in deteriorated specimens. It is concluded that the zinc spot test deserves at least the same place as the acid phosphatase test in the primary investigation of suspected semen stains and might well be the test of choice in older and poorly preserved stains.     

A more sensitive modification of the zinc test for seminal traces suitable for stable test paper strips.

A more sensitive modification of the zinc test for semen has been developed, which can be used either as a solution or incorporated into test papers. The latter retain their sensitivity for at least 3 months.     

The forensic identification of semen by isoelectric focusing of seminal acid phosphatase.

An isoelectric focusing technique for the separation of acid phosphatases is described. The focusing patterns for semen and vaginal secretion are examined in detail and the technique is evaluated as a means of identifying and distinguishing between these body fluids and other materials of potential forensic interest. The method can reliably be used to diagnose the presence of semen in stains and in the post-coital vagina.     

The simultaneous identification of seminal acid phosphatase and phosphoglucomutase by starch gel electrophoresis

Although elevated acid phosphatase (AP) activity in vaginal fluid is a consistent indicator for semen, differentiation between vaginal AP and seminal AP provides a more meaningful result. Detection of seminal AP in mixtures of vaginal AP, feces, and blood is accomplished by starch gel electrophoresis, employing the substrate thymolphthalein monophosphate as a selective visualization agent. Genetic phosphoglucomutase isoenzymes are simultaneously separated by this method and allow differentiation in some semen/vaginal fluid mixtures.     

gamma-Glutamyltransferase test as a new tool for identification of seminal stains

A simple qualitative method for identification of seminal stains based on a high activity of gamma-glutamyltransferase (gamma-GTP) in human semen is described. It employs the release of alpha-naphthylamine from N-gamma-glutamyl-alpha-naphthylamide by the gamma-GTP action: alpha-naphthylamine couples with Fast Garnet GBC salt to produce a strong brownish-red color. The data on its simplicity, specificity, and stability show that the present method is suitable for medicolegal examination of seminal stains as a preliminary test.     

Evaluation of the modified zinc test and the acid phosphatase test as preliminary screening methods in sexual assault case material.

The modified zinc test and a commercially available acid phosphatase test were compared as to their screening parameters according to the microscopical finding of spermatozoa in cases of alleged sexual assault. The study involved 65 pieces of evidence material. It was found that the modified zinc test has a higher sensitivity and higher predictive values than the acid phosphatase test. However, when both tests are combined in parallel, the sensitivity and the negative predictive value could be raised to 99%. This finding suggests that a negative result obtained from the parallel combination of the modified zinc test and the acid phosphatase test predicts very well that no spermatozoa will be found at microscopical examination. Since the latter technique is the only one to give absolute proof of the seminal origin of stains or traces, the parallel combination of the zinc test and the acid phosphatase test might be useful in sorting out these cases or materials that deserve further investigation by more elaborate techniques.     

Zinc test as a new tool for identification of human seminal stains

An extremely simple qualitative method for identification of seminal stains based on high levels of zinc in human semen is described. It uses reaction of 1-(2-pyridylazo)-2-naphthol with zinc to develop a deep red color. The data are presented on the sensitivity, stability and specificity of the present method. We can recommend it for identification of human semen especially in old or denatured samples.     

Further studies on spot tests and microcrystal tests for identification of cocaine

The presence of cocaine in illicit drug samples is still being determined in some laboratories using spot tests and microcrystal tests. Seventeen chemical species were tested using three different spot tests (Wagner, Marquis, and cobalt thiocyanate followed by stannous chloride reactions) and two microcrystal tests (gold chloride and platinic chloride) to determine whether the results could be differentiated from the results of these tests on cocaine. The data obtained indicated that nine of the 17 compounds gave results similar to those from cocaine using the three spot tests, but that the results from microcrystal testing allowed for differentiation of all nine compounds from cocaine.     

Isoenzyme determinations as aids in the identification of biological traces

The findings are described that were determined after a fatal traffic accident. By means of blood and isoenzyme typing, a piece of tissue adhering to the bottom of a car was ascribed to the victim.     

The use of acid phosphatase test papers for DNA profiling.

The acid phosphatase (AP) test is a routine assay used to screen casework items for the possible presence of semen. This colour test is carried out on filter paper which is retained after testing. Two-year-old AP test papers were found to contain sufficient DNA for short tandem repeat (STR) profiling. Prior to polymerase chain reaction (PCR) amplification, the DNA was preferentially separated into sperm depleted and sperm enriched cell fractions. The implication of these findings for past and present cases is discussed.     

Identification of human semenogelin in membrane strip test as an alternative method for the detection of semen

Semenogelin (Sg), a protein originating in the seminal vesicles and a substrate for prostate specific antigen (PSA or p30), is a useful marker for the identification of semen. And detection of Sg has been available commercially in a membrane test recently. PSA is commonly used to detect semen in forensic significant samples taken from sexual assault cases. The strip PSA test has been available commercially from various manufacturers for many years. In this study, we evaluated two immunochromatographic membrane tests, one for Sg and the other for PSA by analyzing human semen, other human bodily fluids/materials including urine, blood, saliva, sweat, breast milk, vaginal secretion and fecal materials, semen from various animals and forensic casework samples. The data demonstrate that both Sg and PSA strip tests provide rapid and sensitive method for identification of seminal plasma. These results show that the immunochromatographic method for Sg detection is useful for the identification of seminal plasma in forensic samples, an alternative to the method for PSA detection.     

Evaluation of prostate-specific antigen (PSA) membrane test assays for the forensic identification of seminal fluid.

Prostate specific antigen (PSA, also known as p30), a glycoprotein produced by the prostatic gland and secreted into seminal plasma, is a marker used for demonstrating the presence of seminal fluid. Methods for the detection of PSA include Ouchterlony double diffusion, crossover electrophoresis, rocket immuno-electrophoresis, radial immunodiffusion, and ELISA. The extremely sensitive ELISA technique can detect PSA in concentrations as low as approximately 4 ng/mL. However, all these techniques are cumbersome and time consuming to perform in forensic laboratories, especially when only a few samples per week are processed. Various membrane tests are currently used in clinical settings to screen a patient's serum for the presence of PSA at levels greater than 4 ng/mL. In this study we evaluated three immunochromatographic PSA membrane tests by analyzing semen stains stored at room temperature for up to 30 years, post-coital vaginal swabs taken at different time after intercourse, semen-free vaginal swabs, and various female and male body fluids, including urine. The data demonstrate that PSA membrane test assays offer the same sensitivity as ELISA-based tests and provide a rapid approach for the forensic identification of seminal fluid. Furthermore, when the supernatant from a DNA extraction is used for the assay, there is essentially no DNA consumption for determining the presence of PSA in a forensic sample.     

The relevance of false positive acid phosphatase reactions indicative of the presence of seminal fluid from oral and vaginal samples

The Body Fluid Forum of the Association of Forensic Science Providers recognised concerns raised by forensic practitioners regarding the lack of data to inform on the incidence of significant AP (Acid Phosphatase) reactions from vaginal and oral samples, i.e. those which might be misinterpreted as indicating the presence of semen. This is particularly relevant in the light of appeal court rulings regarding the need for data to support evaluations. This paper presents collaborative data on the nature and incidence of AP reactions from vaginal and oral swabs provided by donors. The results demonstrate that caution is required with mid to strong purple AP reactions from direct testing of oral swabs and with mid purple reactions from vaginal swabs. The use of a Bayesian approach to assist with the provision of opinions regarding the presence of seminal fluid is highlighted.     

The LAP test. A new method for identification of seminal stains by a qualitative color reaction of leucine aminopeptidase.

A new simple method for identification of seminal stains is described. It employs a qualitative color reaction based on histochemical technique for demonstration of leucine aminopeptidase (LAP), which is extremely abundant in human semen. The method herein reported (the LAP test) is quite suitable for medicolegal examination of seminal stains as a preliminary test.