The prevalence and persistence of saliva in vehicles

Nucleic Acids Persistence-Benefits and Limitations in Forensic Genetics

The analysis of genetic material may be the only way to identify an unknown person or solve a criminal case. Often, the conditions in which the genetic material was found determine the choice of the analytical method. Hence, it is extremely important to understand the influence of various factors, both external and internal, on genetic material. The review presents information on DNA and RNA persistence, depending on the chemical and physical factors affecting the genetic material integrity. One of the factors taken into account is the time elapsing to genetic material recovery. Temperature can both preserve the genetic material or lead to its rapid degradation. Radiation, aquatic environments, and various types of chemical and physical factors also affect the genetic material quality. The substances used during the forensic process, i.e., for biological trace visualization or maceration, are also discussed. Proper analysis of genetic material degradation can help determine the post-mortem interval (PMI) or time since deposition (TsD), which may play a key role in criminal cases.

A spit in time: identification of saliva stains and assessment of total DNA recovery up to 180 days after deposition

The main aim of this work was to validate the detection of saliva samples from denim, cotton, and polyester fabrics aged up to six months, applying rapid immunochromatographic tests resulting in the analysis of nuclear and mitochondrial DNA recovered. A comparison was also carried out between two saliva detection tests, Laboratory and Crime Scene. 50 μl saliva samples (three per time and test) were deposited on denim, cotton, and polyester fabrics. After 1, 3, 7, 14, 21, 30, 60, 90, 150, and 180 days of storage at room temperature, the samples were recovered by swabbing and detected by SERATEC® Amylase (Laboratory) test and SERATEC® SALIVA CS (Crime Scene) test (SERATEC®, Göttingen, Germany). DNA was isolated from the swab extraction buffer applying a silica-based methodology, and quantified based on fluorescent and human-specific quantifications. Then, it was submitted to STR profiling and mtDNA sequencing. According to our results, saliva stains up to six months after deposition remain valid specimens. The intensity of the bands varied among fabric type and time. Total DNA was successfully recovered from all tested samples, though with the limitations of obtaining partial nuclear DNA profiles from the oldest samples. In contrast, complete characterization of mtDNA was achieved from all samples. Lab and CS tests performed similar on the detection of saliva, as well as, DNA yield and profiling. Future research will be able to expand these results, analyzing the stability of other body fluids and the sensitivity of rapid immunochromatographic tests to detect them.

DNA Transfer in Forensic Science: Recent Progress towards Meeting Challenges

Understanding the factors that may impact the transfer, persistence, prevalence and recovery of DNA (DNA-TPPR), and the availability of data to assign probabilities to DNA quantities and profile types being obtained given particular scenarios and circumstances, is paramount when performing, and giving guidance on, evaluations of DNA findings given activity level propositions (activity level evaluations). In late 2018 and early 2019, three major reviews were published on aspects of DNA-TPPR, with each advocating the need for further research and other actions to support the conduct of DNA-related activity level evaluations. Here, we look at how challenges are being met, primarily by providing a synopsis of DNA-TPPR-related articles published since the conduct of these reviews and briefly exploring some of the actions taken by industry stakeholders towards addressing identified gaps. Much has been carried out in recent years, and efforts continue, to meet the challenges to continually improve the capacity of forensic experts to provide the guidance sought by the judiciary with respect to the transfer of DNA.

On the Identification of Body Fluids and Tissues: A Crucial Link in the Investigation and Solution of Crime

Body fluid and body tissue identification are important in forensic science as they can provide key evidence in a criminal investigation and may assist the court in reaching conclusions. Establishing a link between identifying the fluid or tissue and the DNA profile adds further weight to this evidence. Many forensic laboratories retain techniques for the identification of biological fluids that have been widely used for some time. More recently, many different biomarkers and technologies have been proposed for identification of body fluids and tissues of forensic relevance some of which are now used in forensic casework. Here, we summarize the role of body fluid/ tissue identification in the evaluation of forensic evidence, describe how such evidence is detected at the crime scene and in the laboratory, elaborate different technologies available to do this, and reflect real life experiences. We explain how, by including this information, crucial links can be made to aid in the investigation and solution of crime.