No abstract

Determining the postmortem interval (PMI) is strongly impacted by several variables, which consequently results in inaccuracy in the estimation of PMI used in court trials. A PMI experiment was conducted in Kaohsiung County by disposing a burned pig corpse in the woods. One month later, unexpectedly and interestingly, a homicide case, very similar to this mock study, occurred at a distance of 6 km away from the experimental site. The female victim had been killed and burned. The maggots collected from the victim were identified to be Chrysomya megacephala by morphologic observation and were then confirmed by mitochondrial DNA sequence. A PMI of 50 hours was concluded for the burned human body, based on the information of the maggots from the pig corpse. The murderer was eventually arrested and confessed to the crime. According to his statement, the elapsed time since death was calculated to have been 46 hours. In this case, the PMI was estimated successfully and it was almost precise. It would appear that the more similar the surrounding environment between the mock study and the actual case, the more precise can be the PMI estimation.

No abstract

Chewed betel-quid (BQ) residues are often considered vital biological evidence at crime scenes, since the human DNA extracted from the residues is actually from buccal epithelial cells and can be associated with suspects. BQ-chewing is also a risk factor for oral diseases and/or cancers. Archived medical oral-specimens can be used to identify specific individuals under adverse conditions, although STR markers are known to be unstable in various tumor tissues. This study evaluates the DNA stability of forensic marker systems in BQ-chewers' oral epithelial cells, and in archived clinical specimens of oral cancer patients. The genotypes of oral and paired peripheral blood samples in 200 subjects were compared, using the commercialized typing systems of HLA-DQA1, PM (including LDLR, GYPA, HBGG, D7S8, and GC loci), and AmplFCSTR™ markers (including 9 STR loci and the Amelogenin gene). The 100 healthy BQ-chewers had consistent oral swab and paired blood sample genotypes analyzed with both DQA1/PM and STR marker systems. In the 100 oral cancer patients, one discordant result at D7S8 was found in the 600 DQA1/PMmarker loci, and 25 allelic alterations with expansion or contraction were detected in the 900 STR loci. The findings herein suggest that when cancerous specimens were tested, the HLA-DQA1/PM system with point polymorphism appears more reliable than the STR system with length polymorphism. Our results also indicate that healthy BQ-chewers' oral cotton swabs containing buccal epithelial cells are useful for forensic purposes using the HLA-DQA1, PM, and STR marker systems.

The detection of genetic polymorphism has become increasingly important in forensic science as well as in medical genetics. In this report, we describe a systematic flow chart system for HLA-DQA1 genotyping by an improved PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) method coupled with the PRSM (PCR-mediated restriction site modification) method. This flow chart typing system can easily discriminate between a total of eight reported DQA1 alleles commonly found in Chinese. We have applied this flow chart typing system in a forensic case as well as in the determination of the frequencies of the eight DQA1 alleles in 121 unrelated Taiwan Chinese subjects. Our results show that the flow chart DQA1 genotyping is a simple, fast, and accurate system which, in the future, may be considered as an alternative method for routine individual identification in forensic casework, and for paternity testing and tissue typing in medical genetics.