Detecting DNA from a male perpetrator is the goal in the forensic investigation of most sexual assault cases. Y-chromosome-specific STR typing targets the male DNA and is a useful additional tool in cases that often involve a mixture of male and female DNA. Although many technical aspects of Y-STR testing are parallel to autosomal STR testing, the unilateral (patrilineal) inheritance of the Y-chromosome alleles creates a haplotype of linked loci, and the statistical evaluation and reporting of the results differ significantly. Therefore, the SWGDAM Y-STR Subcommittee was established to deal with all aspects of Y-chromosome-specific testing in forensic casework.
The first meeting of the Y-STR Subcommittee convened on January 15, 2003, in Quantico, Virginia. Jack Ballantyne was elected chairman, and Mechthild Prinz was elected co-chairman.
Table 1: Y-STR Subcommittee Members
||Armed Forces DNA Identification, Rockville, Maryland
||California Department of Justice, Berkeley, California
||Center of Forensic Sciences, Toronto, Canada
||Connecticut State Police, Meriden, Connecticut
|Federal Bureau of Investigation, Quantico, Virginia
||Michigan State Police, Lansing, Michigan
||Minnesota Bureau of Criminal Apprehension, St. Paul, Minnesota
||National Institute of Standards and Technology, Gaithersburg,
||Office of Chief Medical Examiner, New York City, New York
||Orange County Sheriff-Coroner Department, Santa Ana, California
||Oregon State Police, Portland, Oregon
||Phoenix Police Department, Phoenix, Arizona
||University of Central Florida, Orlando, Florida
Adopting 11 Loci
The first official business was recommending a set of Y-STR core loci. The committee voted to adopt the 11 loci listed in Table 2. The decision was based on availability to the scientific community and the large amount of published performance and database information for most of the loci. The committee encourages further study of additional loci as to their suitability for forensic use. The first nine loci compose the European minimal haplotype complement of markers. The decision about the core loci was important to ensure data compatibility and allow for construction of appropriate population Y-STR haplotype databases.
Table 2: Adopted Loci
|1||DYS19||Kayser et al. 1997|
|2 and 3||DYS385||Kayser et al. 1997|
|4||DYS389I||Kayser et al. 1997|
|5||DYS389II||Kayser et al. 1997|
|6||DYS390||Kayser et al. 1997|
|7||DYS391||Kayser et al. 1997|
|8||DYS392||Kayser et al. 1997|
|9||DYS393||Kayser et al. 1997|
|10||DYS438||Ayub et al. 2000|
|11||DYS439||Ayub et al. 2000|
Kayser, M. et al. Evaluation of Y-chromosomal STRs: A multicenter
study, International Journal of Legal Medicine (1997) 110(3):125-133,
Ayub, Q. et al. Identification and characterization of novel human
Y-chromosomal microsatellites from sequence database information,
Nucleic Acids Research (2000) 28(2):e8.
The working group is currently developing Y-STR interpretation and reporting guidelines that will include approaches to the statistical evaluation of Y-STR haplotypes. Other projects include promoting appropriate use of Y-chromosome markers in casework and databases.