Human mitochondrial DNA and nuclear DNA isolation from food bite marks.

OBJECTIVE: Bite mark analysis is used for comparison between bite marks on a bitten object and the suspects' teeth. However, if it is not possible to obtain a correct match, it is important to recover salivary DNA. Previous studies have tried to isolate human nuclear DNA from bitten foods but were not completely successful. In the present work, we studied the efficiency of human nuclear and mitochondrial DNA isolation from bite marks in cheese, a donut and an apple. DESIGN: Using a double swab technique and silica-based DNA extraction kit, nuclear and mitochondrial DNA were isolated. Human housekeeping genes were amplified to analyse the efficiency of nuclear DNA profiling. mtDNA was sequencing and haplogroup assign. RESULTS: Although cheese and apple samples showed the highest concentration of DNA, the purity of DNA on the apple was low. Moreover, apple samples failed to amplify the two human housekeeping genes, GAPDH and RPL22. In contrast, cheese samples have high purity and amplification efficiency. Donut samples showed an intermediate value and low amplification efficiency. In spite of these results, isolation and characterization/sequencing of human mitochondrial DNA was completely successful in the three samples, which pointed out the possibility of identification through this type of DNA. CONCLUSIONS: This research indicated that it is possible to recover and isolate human nuclear and mitochondrial DNA from bitten foods, although the quantity and purity of nuclear DNA depends on the type of food. That is of significance important in forensic sciences for the correct identification of a suspect.

An evaluation of DNA yield, DNA quality and bite registration from a dental impression wafer.

BACKGROUND: The authors determined the amount and quality of the DNA captured by a bite impression wafer and analyzed any inaccuracies in the impression wafer. METHODS: The authors made bite registrations for subjects aged 7 to 12 years by using a dental impression wafer (Toothprints, Kerr, Orange, Calif.), obtained an oral rinse sample, took cheek cells by using buccal swabs and made an alginate impression to pour a stone model. They extracted and quantified the DNA from the dental impression wafer, mouthwash and buccal swabs by using the Quant-iT PicoGreen (Invitrogen, Carlsbad, Calif.) assay and a real-time polymerase chain reaction (RT-PCR) assay. They compared the stone models and imprints from the wafer. RESULTS: The average amounts of DNA determined by using Quant-iT PicoGreen from the buccal swab, mouthwash and dental impression wafer samples were 113.61, 509.57 and 1.03 micrograms, respectively. The average amounts of DNA determined by using RT-PCR from the buccal swab, mouthwash and dental impression wafer samples were 11.5240, 22.2540 and 0.0279 mug, respectively. The bite registrations and stone models had an average of 14 percent of mismatches. CONCLUSION: The dental impression wafers captured DNA but not in high quantities. They did not produce an accurate representation of the dentition. CLINICAL IMPLICATIONS: The dental impression wafers captured enough DNA to permit amplification. The accuracy of the bite registration was not sufficient for identification purposes. Therefore, dental impression wafers may be useful only as a reservoir for DNA.

A look at forensic dentistry--Part 2: teeth as weapons of violence--identification of bitemark perpetrators.

Teeth are often used as weapons when one person attacks another or when a victim tries to ward off an assailant. It is relatively simple to record the evidence from the injury and the teeth for comparison of the shapes, sizes and pattern that are present. However, this comparative analysis is often very difficult, especially since human skin is curved, elastic, distortable and undergoing oedema. In many cases, though, conclusions can be reached about any role a suspect may have played in a crime. Additionally, traces of saliva deposited during biting can be recovered to acquire DNA evidence and this can be analyzed to determine who contributed this biological evidence. If dentists are aware of the various methods to collect and preserve bitemark evidence from victims and suspects it may be possible for them to assist the justice system to identify and prosecute violent offenders. This paper reviews the recognition and recovery of this evidence and provides insight into modern methods used to investigate bitemark evidence from heinous crimes.

PCR-based DNA typing of saliva stains recovered from human skin.

Human bites in cases of homicide, sexual assault, and abuse are often distorted due to the elasticity and curvature of the skin. Physical comparison of a bite mark to a suspect's teeth is sometimes difficult. Saliva, which is usually deposited during biting, can be collected and analyzed to identify the perpetrator. Using simulated bite mark situations in two experimental series, three samples of 40 microL of whole saliva were deposited on the skin of 27 cadavers (at 33 sites) and three samples of 100 microL of whole saliva were deposited on the skin of 5 cadavers (at 12 sites). Saliva was collected using the double swab technique at t = 5 min, t = 24 h, and t = 48 h. DNA was extracted using the modified Chelex method and submitted to PCR-based typing at two short tandem repeat loci. Results indicate that the concentration of DNA in saliva recovered from skin varies as a function of time since deposition. There is a significant decrease in concentration in the first 24 h but the concentration remains stable from 24 to 48 h. The success of PCR amplification is independent of the time since deposition or the concentration of DNA in the saliva sample. Contamination from the DNA of the cadaver was not found in any of the cases studied.