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像《永利app新版本官网地址》和《永利app新版本官网地址》这样的电视剧让刑事调查看起来很容易. In real life, DNA测试具有挑战性，需要昂贵的设备, special facilities and extensive training to identify DNA from a crime scene and determine which belongs to a potential suspect and which may have been transferred from someone who was never there. Research from the University of New Hampshire has found a less expensive and easier-to-use test to learn more about forensic touch DNA. This research has important implications for forensic investigations and being able to identify DNA from a primary contact — someone who may have committed the crime — as well as secondary DNA that was inadvertently and indirectly transferred through touch.

“So-called ‘touch DNA’ is a form of trace DNA that is deposited when a person touches something and leaves behind their skin cells, 汗液或其他含有它们DNA的液体,” said Samantha McCrane, a lecturer in anthropology and co-director of UNH’s Forensic Anthropology Identification and Recovery (FAIR) Lab. “而接触DNA通常是直接接触的结果, which we call primary transfer, 它也可以在物体表面或个体之间间接传递, 留下了二级甚至三级DNA.”

In their study, 最近发表在《永利app新版本官网地址》上, researchers developed an innovative test that uses a more accessible and affordable sequence method, known as qPCR. To test their protocol, 他们将男性和女性志愿者配对，并保持简单, 只看一个标记来确定DNA的性别. In the trials, they first had a male participant hold a gun grip for 30 seconds before placing it down on a sterilized table. Then, a female picked up the same gun grip and held it for 30 seconds and followed that by grasping a coffee cup for 30 seconds. Afterward, the gun grip, coffee mug and female's hand were all swabbed for DNA.

The findings with the new method found male and female DNA on the gun grip in 71% of the trials indicating primary transfer since both participants directly touched the gun grip. 在50%的试验中，在女性的手上发现了男性DNA, representing secondary transfer since the DNA was transferred indirectly from the gun grip. 咖啡杯上男性DNA的记录率为27%, indicating tertiary, or third level, transfer since the DNA was indirectly transferred from the gun grip to the female's hand and finally to the coffee mug.

“The challenge with transfer DNA is that it opens up the dangerous possibility of DNA ending up on items or victims at a crime scene that a person may not have touched” said McCrane. “This has occurred in multiple cases, 导致无辜的人因他们没有犯下的罪行而受到指控.”

The study also looked at the potential effects of age, ethnicity and skin conditions on DNA transfer. Ethnicity and age did not appear to affect touch DNA deposits and the small sample of those with sloughing skin conditions, like eczema, 没有显示出与原代DNA转移有任何显著关联.

Researchers say even DNA experts cannot distinguish between different types of DNA transfer and this understudied field lacks enough data to fully understand which variables affect direct versus indirect DNA transfer and how often it happens. These new study results contribute to a better understanding of the conditions under which secondary and tertiary DNA transfer occurs and researchers are hopeful this new inexpensive protocol could lead to more research allowing for greater sample sizes and replication runs.

Co-author on the study was Connie Mulligan, professor of anthropology at the University of Florida.