Abstract: Objective To establish a query table of IBS critical value and identification power for the detection systems with different numbers of STR loci under different false judgment standards. Methods Samples of 267 pairs of full siblings and 360 pairs of unrelated individuals were collected and 19 autosomal STR loci were genotyped by GoldeneyeTM 20A system. The full siblings were determined using IBS scoring method according to the ‘Regulation for biological full sibling testing’. The critical values and identification power for the detection systems with different numbers of STR loci under different false judgment standards were calculated by theoretical methods. Results According to the formal IBS scoring criteria, the identification power of full siblings and unrelated individuals was 0.764 0 and the rate of false judgment was 0. The results of theoretical calculation were consistent with that of sample observation. The query table of IBS critical value for identification of full sibling detection systems with different numbers of STR loci was successfully established. Conclusion The IBS scoring method defined by the regulation has high detection efficiency and low false judgment rate, which provides a relatively conservative result. The query table of IBS critical value for identification of full sibling detection systems with different numbers of STR loci provides an important reference data for the result judgment of full sibling testing and owns a considerable practical value.

Key words: forensic genetics, sibling relations, short tandem repeat, identity by state （IBS）