Forensic Biology and Biological Fluids

Delivery of Evidence for Laboratory Testing 

The evidence will be delivered in evidence bags. Collection of evidence samples can be done using gloves to avoid contact with the evidence and in the process contamination of the samples. The broken glass can be placed in the evidence bags especially in the areas which have fingerprints of the culprits of the crime committed. Stains from the carpet can also be collected and put in a different container. Clothes can be encased in a bag and furniture encased using polythene and carried to forensic testing labs. The drinking glasses can be put in evidence bags. Therefore, the evidence is supposed to be sealed and labeled with the movements documented with all the vigilance required. The rules of transportation and placement of evidence into custody have to be adhered to for proper admission in the courtroom. 

Testing Body Fluids before Admitting as Evidence 

Blood 

Blood can be tested using chemicals that rely on the catalytic activity that takes place through the heme groups in the hemoglobin. The tests that can be undertaken are the leucomalachite green test which is less sensitive but specific, tetramethylbenzidine, and the Kastle-Meyer test which is quite sensitive and highly accurate. Some of the criteria which can be administered for confirmatory purposes though impractical are the microscopic identification of cells and crystal tests. 

Semen 

The location of semen can be done using the presumptive test used to detect phosphatase which is secreted by the prostate glands. The analysis is performed using the Brentamine Fast Blue reagent. Confirmatory crystal tests are used in the detection of semen like the Florence test due to the formation of the choline crystals. The other conventional methods that have been adopted are the semi quant tests even though they have false positives with the presence of other elements such as breast milk, urine, and vaginal fluids. 

Saliva 

The test for the presence of saliva that is commonly used presumptively is the phadebas test. The analysis is based on its ability to detect the presence of alpha-amylase. The alternative test that is used is the SALIgAE test. The test is colorimetric and has more sensitivity. 

A positive test for each of the samples indicates the presence of the sample in question. However, a mixture of the tested sample with other fluids can give a false positive to suggest that what is being tested is present falsely. In the case of blood, positive results for leucomalachite green test indicate that blood is present in the sample. The Florence test can give a positive implied by the formation of the choline crystals to indicate the presence of semen. The SALIgAE test is used to detect the presence of alpha-amylase which is determined to be present by a positive indication of the test. 

The tests are very similar because of the use of reagents to confirm the presence of individual samples. They are also capable of giving false positives which give a wrong signal about the presence of a tested sample. The false positives are mainly due to the presence of other fluids in the sample that is capable of contaminating the samples and hence giving the false positives seen. 

The tests are different because they look for various components in the sample to confirm the presence of the respective elements. For instance, the blood test relies on the catalytic activity of the heme in hemoglobin; the semen test is used to detect phosphatase while the saliva test is used to detect the presence of alpha-amylase. 

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