Innocent of the crime under investigation: suspects’ counter-interrogation strategies and statement-evidence inconsistency in strategic vs. non-strategic interviews

ABSTRACT

The study examines the counter-interrogation strategies applied by mock suspects (N?=?94), who are innocent of a mock crime under investigation but who were present at the scene, for different reasons, at around the time the crime occurred. Half were present at the crime scene to carry out a lawful act, the other half to carry out an unlawful act. Furthermore, this study examines the effect of the Strategic Use of Evidence (SUE) technique as a strategic interviewing technique (vs. a non-strategic technique), on suspects’ statement-evidence inconsistencies. Participants were randomly assigned to the two interview conditions (strategic vs. non-strategic) and were interviewed as suspects of a crime, which none of them had committed. The results show that the most commonly used counter-interrogation strategy in both groups was to be honest. However, 26.1% of the innocent suspects, performing an unlawful act, reported the strategy to be deceptive. In addition, the statements of suspects executing an unlawful act were significantly more inconsistent with the evidence in the strategic than the non-strategic interview condition. The increased statement-evidence inconsistency rates potentially put these suspects at risk of being assessed as guilty of a crime they did not commit.     

浓缩DNA法结合miniSTR分型技术检验微量DNA

目的优化低拷贝数DNA STR分型方法。方法对采用磁珠法或Chelex-100法提取DNA,Identi-filer试剂盒扩增,未获得分型结果的日常检案检材,采用物理浓缩法或过柱浓缩法浓缩DNA,采用miniFilerTM试剂盒再次扩增分型。结果 127例检材中,47例磁珠法提取DNA未获得分型的样品,分型成功率为36%;80例Chelex-100法提取DNA未获分型的样品,分型成功率为30%。结论采用浓缩法和miniFilerTM试剂盒,可以提高日常检案中低拷贝数检材的STR检验分型成功率。     

Could Secondary DNA Transfer Falsely Place Someone at the Scene of a Crime?,

The occurrence of secondary DNA transfer has been previously established. However, the transfer of DNA through an intermediary has not been revisited with more sensitive current technologies implemented to increase the likelihood of obtaining results from low‐template/low‐quality samples. This study evaluated whether this increased sensitivity could lead to the detection of interpretable secondary DNA transfer profiles. After two minutes of hand to hand contact, participants immediately handled assigned knives. Swabbings of the knives with detectable amounts of DNA were amplified with the Identifiler^® Plus Amplification Kit and injected on a 3130xl. DNA typing results indicated that secondary DNA transfer was detected in 85% of the samples. In five samples, the secondary contributor was either the only contributor or the major contributor identified despite never coming into direct contact with the knife. This study demonstrates the risk of assuming that DNA recovered from an object resulted from direct contact.