If male A has a Y-STR haplotype that matches the Y-STR profile found in an unknown sample, then male A cannot be excluded as being the donor to that unknown sample. In addition, all patrilineal relatives of male A cannot be excluded. It may also be true that an unknown number of unrelated males may not be excluded as being the donor of that unknown sample.
There are many scenarios in which the Y-STR test may be used. To determine if this test will be helpful in your particular situation, please contact us or call 800-DNA-EXAM (800-362-3926). One of our case consultants will review your particular situation and guide you through the testing process.