Background: Deaths occuring without a known disease and/or a known cause, deaths with non-lethal diseases are interpretated as sudden-unexpected-suspected deaths. Autopsy should always required to evaluate the cause of death. Some of the cases can be termed as negative autopsy since the cause of death can not be determined. This is one of the main interests of the future forensics. Molecular autopsies are one of the main practices of to reduce the negative autopsy ratios. Thus, post-mortem KCNQ1 genetic variation tests are done in sudden unexpected death cases.
 Material and methods: In this study 0 – 50 years old sudden-unexpected deaths autopsy cases were handled. Samples taken from cases were evaluated and “KCNQ1” genetic variation tests were done in our Department.
 Results: This study included 47 cases of 42 sudden unexpected death cases (0 – 50 age group) and 5 control group. 15 cases were between 40 – 50 age group and number of cases were increasing with age. 29 of cases (% 69) were male. Evaluation of body-mass index of cases were done and normal weighted cases were the most common with 21 cases (% 50). According to death locations; 17 cases had died (% 45,9) at home. Death location records of 5 cases couldn’t be found. Pathological examinations of all cases were done. We had identified fibrosis and fatty change appearances in SA node of 9 cases (% 21,4) and AV node of 13 cases (% 30,9) especially in conduction tissue examinations. As the result of KCNQ1 genetic analysis of cases, we identified sequence variations in 1638th nucleotid of exon 13 and 1986th nucleotid of exon 16.
 Conclusion: Cases with conduction system pathology and sequence variations of KCNQ1 genetic analysis shows that we are in need of these tests among routine practice to reduce negative autopsy ratios.
 Key words: KCNQ1, molecular autopsy, sudden unexpected death, conduction system, negative autopsy.