Journal Published Online: 01 September 2004
Volume 49, Issue 5

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



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.

Author Information

Leclair, B
National DNA Data Bank, Ottawa, Ontario, Canada Current address: Myriad Genetic Laboratories, Inc., Salt Lake City, Utah
Fregeau, CJ
National DNA Data Bank, Ottawa, Ontario, Canada
Bowen, KL
National DNA Data Bank, Ottawa, Ontario, Canada
Fourney, RM
National DNA Data Bank, Ottawa, Ontario, Canada
Pages: 13
Price: $25.00
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Stock #: JFS2003312
ISSN: 0022-1198
DOI: 10.1520/JFS2003312