Table of contentsAbstract DNA fingerprintsDNA traceDNA testing and the lawAbstract DNA can be transferred by touch. This tactile DNA is used to obtain useful information in criminal investigations, identification of disaster victims or even missing persons (Sankhla and Kumar, 2017). The significant value of DNA profiling has increased over time in forensic investigations and this has helped develop the technology to extract DNA and obtain information via DNA profiling from small quantities. There are many variables that influence DNA deposition upon touch, such as the type of surface, the nature of the contact, and the shedder state. Variables such as pressure have been shown to increase the transfer of DNA between two surfaces. Can pressure affect DNA deposition directly from skin onto an object? Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essayAn experiment that studied the impact of pressure and its effects on the quantity and quality of DNA deposited by touch. The experiment involved participants applying expert pressure with their fingertips to a DNA-free polycarbonate placed on top of a scale for one minute. All five fingerprints were swabbed as a single sample and DNA was extracted, quantified, and profiled (Tobias et al., 2017). To exert a pressure of 4, 21, or 37 kPa, the combined area of ​​the fingertips was used and the weight to push the scale with that would produce the desired pressure for each hand was determined. Both the left and right hands were used by the volunteers in random order for three non-consecutive days. The results showed a correlation between the pressure between the skin and the surface and the amount of DNA deposited. As the pressure increased, the deposited DNA increased. This resulted in the detection of multiple alleles from the volunteer and from unknown sources. The days or hands for which (left or right) the DNA sample was collected from the polycarbonate showed no significant differences in DNA quantity, although pressure at 21 and 37 kPa showed significant differences in DNA quantity between individuals . These results provide great insight into the impact of pressure on DNA deposition and show that pressure is an important variable and should be taken into account during a criminal investigation when prioritizing surfaces or objects. The shredding capacity is different for each individual. One experiment investigated factors affecting the transfer of DNA onto handled objects, and a process called "shredding" involved volunteers holding sterile plastic tubes. Any material transferred to the tube was blotted and amplified using STR profiles generated using AmpFISTR SGM PlusTM. These volunteers were asked to hold the tube in each hand and participate in a series of hand washing experiments. The profiling results were compared in an attempt to characterize the type of shredding. The main purpose was to test whether a person is a "good shredder" or a "bad shredder". The results showed many variables influencing trituration, some variables influenced trituration significantly, such as the hand the tube was held in, as well as the time since the last hand was washed. Thus, they concluded that it was complicated to characterize an individual as a "good" or "bad" shredder. 60 were used in this experimentvolunteers and none of them were really "good" shedders and if there were any "good" shedders they would be rare to find. In terms of trituration, it would be difficult to apply this variable to each case individually and therefore should be used as a general baseline for interpreting trace DNA evidence. Secondary transfer is one of the frontiers in forensic DNA research. Secondary transfer occurs when a person's DNA is passively transferred onto an object by someone or something else. Sources such as skin cells are responsible for depositing small amounts of trace amounts of DNA on an object after it has been touched or used. The chances of placing an individual who may be innocent at the crime scene increase if an object with such a trace of DNA is found and taken as evidence for a crime investigation. The issue of contamination by secondary transfer is now a matter before the courts and its importance is increasing. Experiments are underway to detect secondary DNA samples. Transferring DNA through an intermediate source has not been tested using currently used technologies that are implemented to increase the chances of obtaining results from low-template, low-quality samples. One experiment was DNA to see if these sensitive current technologies could detect interpretable secondary DNA. This experiment involved body-to-body contact where participants held hands for two minutes and then immediately handled knives. The DNA collected from the knife swabs was amplified. DNA typing results showed that 85% of the samples had a secondary DNA contributor who did not directly touch or handle the knife. In 5 samples the secondary DNA contributor was the main or only contributor despite not being in contact with the knife (Kokshoorn et al., 2016). This showed that assuming DNA on an object is due to direct contact can be risky and can put someone in the wrong position. (RFLP) technique for creating a “DNA fingerprint”. RFLP is a technique in which DNA is cut where a specific sequence of bases occurs using restriction enzymes. This gave small pieces of DNA of varying lengths. This was a major innovation for forensic science as it allowed specific profiles to be created for an individual. The use of this technology and technique required the presence of a large amount of DNA to create a fingerprint. This caused a serious problem for forensic samples, one of the other major drawbacks was that it was a time-consuming process that is not readily available during a criminal investigation and was also labor intensive. Kerry Mullis invented the polymerase chain reaction (PCR) in 1986 which improved the efficiency of DNA testing. VNTR analysis improved with the introduction of PCR as it allowed the analysis of small amounts of DNA. Using VNTR with PCR causes problems such as amplification of shorter alleles, but longer alleles were not detected and were not amplified. This led to the discovery of short tandem repeats (STRs). These were much smaller than VNTRs and thus were all efficiently detected and amplified. The transition from VNTRs to STRs for DNA analysis has made it possible to successfully analyze degraded DNA and track DNA significantly faster. The increased sensitivity of PCR made it susceptible to contamination and therefore strict protocols were followed when using PCR. Due to the smaller numberof alleles in STRs, mineral loci were needed to produce information about the likelihood of two people sharing a profile and so the multiplex STR system was introduced. This system allowed many STR loci to be analyzed simultaneously. Using fluorescent labels, automated sequencing technology, and commercial STR kits, PCR-STR technology has become the preferred technology for use in forensic laboratories. Trace DNA Trace DNA sample is a sample that falls below the recommended threshold at any stage during its analysis, this ranges from sample collection, through to profile interpretation as defined by Van Oorschot et al. (2010). Terms such as tactile DNA, low-template DNA (LT-DNA), low-copy-number DNA (LCN-DNA), and low-level profile are used interchangeably. All the above terms, although used interchangeably, have different relevance at different stages during DNA analysis (Van Oorschot et al., 2010). The term Touch DNA refers to the minute amount of DNA collected and/or extracted while the low model defines the tiny mount of DNA material used during the amplification phase; a low copy number refers to the increase in the number of cycles during amplification rather than the amount of DNA material, a profile is defined as low level when the peak heights are below the validated threshold level. To improve the sensitivity of the standard PCR method, a simple technique is used. This is where the number of cycles is increased from 28 to 34. This increased sensitivity of the LCN technique in increasing cycles allowed the recovery of DNA from touched surfaces. The implication of the use of this technique has increased the evidentiary value of the elements collected at crime scenes. Previously, DNA testing was primarily used to help solve crimes such as murder and rape, but with the ability to detect "DNA smudge" from evidence collected at crime scenes such as robberies, break-ins and hijackings it has enabled the recovery and DNA typing. which in turn allowed for greater recovery of DNA from more types of evidence, such as from masks worn on the face during the robbery to bite marks left on rape or murder victims. The LCN-DNA technique, although providing greater sensitivity, has its drawbacks. Increasing the number of cycles during PCR results in broader stutter peaks, allele drops in and/or out, heterozygote imbalance, loci dropouts, and the appearance of unknown allele peaks or contamination. Contamination can occur at any time during and within the chain of custody, this is the transfer of DNA after the crime event. A small amount of DNA contamination is not a big problem when dealing with large amounts of DNA input, but it plays an important role and has a greater impact when dealing with low-level DNA analysis. template. LCN DNA analysis is practiced by most forensic laboratories, the strength of evidence derived from this type of DNA analysis is diminished compared to conventional methods of DNA analysis. This is due to uncertainties surrounding the method of DNA transfer and how and when the DNA was transferred along with the interpretation and reporting of the results obtained (Linacre, 2009). Foster et al. (2008) investigated other methods that can be used to improve 28-cycle PCR to reduce problems resulting from increasing the number of PCR cycles. From their study they concluded that by combining PCR product cleanup, concentration, increased sample loading along with increased injection parameters, profiles were produced from the 28-cycle PCR.