Body fluid identification is fundamental in forensic science as it links a specific biological source to a genetic profile, thus providing critical clues for crime scene reconstruction. Blood is one of the most common body fluids found on the crime scene, and several strategies have been developed for its identification in recent decades. Usually, after a preliminary (or presumptive) test to determine the presence of blood (both human and non-human), a confirmatory test is needed to prove that the sample is human blood. Out of the confirmatory tests, immunochromatographic (IC) assays are the most commonly and widely used. This work gives a review of the use of commercial kits specifically developed to detect human hemoglobin or glycophorin A (a surface protein of human red cells) in forensics. Claimed sensitivity varies broadly (ranging from 0.06 to 75 nanoliters of fresh blood), but different values (as low as 0.002 nL) were found during validation procedures. Specificities are high, and the possibility of cross-reaction (with the risk of false-positive results) is so low that it can be considered negligible. False-negative results, however, can be found due to the so-called “hook effect” as well as to the target degradation/modification, which interferes with the Ag-Ab binding. In addition, the chemical compositions of the presumptive test, detergents, and washing can also promote false negative outcomes in peculiar situations. Although IC assays are rapid, inexpensive, specific, and easy to use even on the crime scene, their major limitation is represented by the destructive approach required by this kind of confirmatory test. Since the final goal of the forensic investigation is the genetic typing of a bloodstain, we will describe the strategies developed for IC assays of faint stains as well as the strategies adopted to ensure that exactly the same sample undergoes human blood identification and DNA typing.

Dried urine spots (DUS) represent a potential alternative sample storage for forensic toxicological analysis. The aim of the current study was to develop and validate a liquid chromatographic tandem mass spectrometric procedure for the detection and quantitative determination of cannabinoids and metabolites in DUS. A two-step extraction was performed on DUS and urine samples. An LC-MS/MS system was operated in multiple reaction monitoring and positive polarization mode. The method was checked for sensitivity, specificity, linearity, accuracy, precision, recovery, matrix effects and carryover. The method was applied to 70 urine samples collected from healthy volunteers and drug addicts undergoing withdrawal treatment. The method was successfully developed for DUS. LODs lower than 2.0 ng/mL were obtained for all the monitored substances. All the validation parameters fulfilled the acceptance criteria either for DUS or urine. Among the real samples, 45 cases provided positive results for at least one compound. A good quali-quantitative agreement was obtained between DUS and urine. A good stability of THC, THCCOOH and THCCOOH-gluc was observed after a 24 h storage, in contrast to previously published results. DUS seems to provide a good alternative storage condition for urine that should be checked for the presence of cannabinoids and metabolites.