传统上在法医证据恢复过程中使用的DNA检索方法,包括擦拭和胶带提起,在多孔材料上使用时效果有限,粗糙的基材,如砖和地毯。这可能是由于DNA材料被分散并且对于表面采样技术是不可达的。在此评估中,我们调查了微生物湿真空系统(M-Vac®;M-Vac®系统,Inc.,桑迪,UT),因为据报道,从具有挑战性的展品中检索到更多的DNA材料。进行了四阶段评估,首先用已知供体唾液在两个稀释液中播种地毯和砖基底,并比较胶带提升的DNA回收率,擦拭,和M-Vac®。然后模拟地毯上的受害者挣扎场景,以比较每种方法的痕量DNA回收率。还进行了两种模拟场景;一件衬衫被淹没在小溪床上五天,以采样穿着者的DNA,并对汽车行李箱进行了采样,以评估从通常的汽车乘员的背景DNA中恢复受害者DNA的可能性。最后,通过比较过滤器子采样方法,针对新南威尔士州(澳大利亚)辖区使用的全自动DNA裂解和提取平台,优化了M-Vac®采样过程的兼容性。该研究的结果是混合的。对于砖块,没有一种收集方法能有效地检索DNA.在地毯上,M-Vac®从唾液接种的样本中检索到最大量的DNA,然而,胶带提升优于所有“触摸”DNA恢复方法。M-Vac®从从小溪床上回收的T恤中回收了最大量的DNA,因为它能够回收嵌入的DNA。最后的模拟案例汽车靴场景导致从磁带升降机中恢复了更多的受害者DNA,M-Vac®更有可能回收太弱和/或复杂而无法解释的混合物。最后,讨论了有关M-Vac®系统与全自动DNA裂解和提取的兼容性的操作考虑因素。考虑到部署M-Vac®的大量时间和成本,建议仅在擦拭和胶带提升方法未能产生足够的DNA材料后才在案例工作中使用,其中底物属性可能会受益于M-Vac®检索嵌入DNA的利基能力,和低水平的背景DNA可能是预期的。
DNA retrieval methods traditionally used during forensic evidence recovery including swabbing and tape lifting, can have limited effectiveness when used on porous, rough substrates such as bricks and
carpet. This is possibly due to the DNA material being dispersed and unreachable for surface sampling techniques. In this evaluation we investigated the effectiveness of the Microbial Wet-Vacuum System (M-Vac®; M-Vac® Systems, Inc., Sandy, UT), as it has been reported to retrieve greater amounts of DNA material from challenging exhibits. A four-stage evaluation was conducted, starting with seeding
carpet and brick substrates with a known donor\'s saliva in two dilutions and comparing the DNA recovery of tape lifting, swabbing, and the M-Vac®. A victim struggle scenario on
carpet was then mimicked to compare trace DNA recovery by each method. Two mock scenarios were also conducted; a shirt was submerged in a creek bed for a period of five days to sample for the wearer\'s DNA, and a car boot was sampled to assess the possibility of recovering a victim\'s DNA amongst background DNA from the usual car occupants. Finally, the compatibility of the M-Vac® sampling process was optimised for the fully automated DNA lysis and extraction platforms used in the NSW (Australia) jurisdiction by comparing filter subsampling methods. The results from the study were mixed. For bricks, none of the collection methods were effective in retrieving DNA. On
carpet, the M-Vac® retrieved the greatest quantities of DNA from the saliva-seeded samples, however, tape lifts outperformed all methods for \'touch\' DNA recovery. The M-Vac® retrieved the greatest amount of DNA from the t-shirt recovered from a creek bed as it was able to retrieve the embedded DNA. The final mock case car boot scenario resulted in greater victim DNA recovery from tape lifts, with the M-Vac® more likely to recover mixtures too weak and/or complex to be interpreted. Finally, operational considerations regarding the compatibility of the M-Vac® system with fully automated DNA lysis and extraction are discussed. Considering the substantial time and cost to deploy the M-Vac®, it is recommended to be utilised in casework only after swabbing and tape lifting methods have failed to yield sufficient DNA material, where the substrate properties would likely benefit from the M-Vac\'s® niche capabilities for retrieving embedded DNA, and low levels of background DNA may be anticipated.