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Touch DNA is a forensic method for analysing DNA left at the scene of a crime. It is called "touch DNA" because it only requires very small samples, for example from the skin cells left on an object after it has been touched or casually handled.〔(Low Copy Number DNA ) - nfstc.org〕 Touch DNA analysis only requires seven or eight cells from the outermost layer of human skin. The technique has been criticized for high rates of false positives due to contamination — for example, fingerprint brushes used by crime scene investigators can transfer trace amounts of skin cells from one surface to another, leading to inaccurate results.〔(Low Copy Number DNA and The Forensic Institute )〕 Because of the risk of false positives, it is more often used by the defense to help exclude a suspect rather than the prosecution. The technique is very similar to Low Copy Number DNA analysis, to the extent that court rulings have sometimes confused the two.〔(Disagreement on What to Call DNA Profiling with Really Small Samples Confuses Courts ) - Penn State University〕 In LCN DNA analysis, the DNA goes through additional cycles of PCR amplification.〔 ==Notable cases using Touch DNA== *Dutch born DNA analysts Richard and Selma Eikelenboom used touch DNA in the exoneration of Tim Masters in 2008. Masters had been convicted of the murder of Peggy Hettrick and sentenced to life in prison in 1999. The Eikelenbooms have worked on a number of high-profile cases, including the murders of Caylee Anthony and JonBenet Ramsey.〔(Touch DNA from DNA Forensics )〕 * The duct tape found with the remains of Caylee Anthony was tested for the presence of touch DNA during the criminal case against her mother, Casey Anthony. Richard Eikelenboom testified for the defense that none of Caylee's DNA was found on the tape. * Touch DNA was introduced in the third trial of David Camm by the defense. The DNA profile of another man, Charles Boney, was found on a number of objects at the crime scene, including the panties of Camm's wife Kim and a fingernail that is thought to have broken off during the struggle. The DNA evidence aided in his acquittal of the murders. * In 2008, the parents of JonBenet Ramsey were cleared as suspects in her 1996 murder following an analysis of touch DNA on her clothing. The family had long been the target of suspicion by the media, the police, and the public in the death of 6 year old JonBenet. The DNA also cleared John Mark Karr, a teacher who was arrested for the murders in 2006. The DNA was determined to belong to an unknown male. The case remains unsolved. * The prosecution used touch DNA to help build their case against James Biela for the murder of Brianna Denison. Touch DNA was collected from the doorknob of the residence where Brianna was staying when she was abducted. A DNA sample obtained from panties found near the body was later matched to the touch DNA and to Biela himself. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Touch DNA」の詳細全文を読む スポンサード リンク
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