ISSN: 0022-1198
CODEN: JFSCA
Published Online: 1 September 2004
Page Count: 13

Systematic Analysis of Stutter Percentages and Allele Peak Height and Peak Area Ratios at Heterozygous STR Loci for Forensic Casework and Database Samples
Leclair, B

Fregeau, CJ
National DNA Data Bank, Ontario

Bowen, KL
National DNA Data Bank, Ontario

Fourney, RM
National DNA Data Bank, Ontario

(Received 13 September 2003; accepted 24 April 2004)

Abstract

To assist the interpretation of STR DNA typing results from forensic casework samples containing mixtures, the range of heterozygous allele peak height and peak area ratios (HR) and stutter percentages (stutter %) for the loci comprised in the AmpFℓSTR® Profiler Plus™ (PP) kit were assessed on 468 database and 275 casework single source samples. Stutter % medians were similar for database and casework samples, ranging from 2% to 7%. The upper limit of the stutter value range was 16%, calculated as median +3 SD, although lower locus-specific values could be used. HR medians were 93 ± 6.5% for database samples, 88 ± 12% for casework samples. For casework samples, the maximum signal imbalance noted was 52%, calculated as median -3 SD. No significant difference was observed between peak height and peak area calculated values. This study shows the importance of selecting the proper reference database for the establishment of HR threshold values.

Keywords:
forensic science, casework, STR, stutter, heterozygous allele ratio, interpretation

Paper ID: JFS2003312
DOI: 10.1520/JFS2003312
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