[Effect of Benzidine Test on DNA Analysis of Bloodstain]

To explore the effect of benzidine test and related reagents on DNA analysis of bloodstain.

A total of 970 bloodstain filter paper samples with 1 μL venous blood were collected, and 10 of them acted as control samples. After benzidine test and related reagent processing, DNA of 960 samples was extracted by Chelex-100 and silica bead methods and then multiplex amplified by AmpFℓSTR™ Identifiler™ Plus PCR kits. The results of STR typing were compared between different groups.

DNA were extracted immediately after benzidine test. Totally STR loci （3.80±1.34） were detected by silica bead method, while no STR loci were obtained by Chelex-100 method. Thirteen samples （21.7%） with whole STR typing results were obtained by drying after benzidine test, and the STR locus number （12.90±1.49） which obtained by silica bead method was much higher than by Chelex-100 method （4.70±1.96） （P<0.05）. When DNA was extracted immediately after the addition of glacial acetic acid, the STR locus number was （9.40±2.09） by silica bead method, but no STR typing result was obtained by Chelex-100 method. All 15 STR loci could be obtained by only adding glacial acetic acid after drying and only adding tetramethylbenzidine alcoholization liquid or 3% hydrogen peroxide liquid.

Benzidine test has significant influence on DNA analysis of bloodstain. The Chelex-100 method is not suitable for the DNA extraction of bloodstain after benzidine test. Drying after benzidine test and silica bead methods can effectively enhance the STR locus number of bloodstain.