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Y-STR Testing: Enhancing Sexual Assault and Cold Case Workflows

NCJ Number
Date Published
February 2018
2 pages
This instructional resource brief for jurisdictions participating in the U.S. Justice Department's Bureau of Justice Assistance's (BJA's) Sexual Assault Kit Initiative (SAKI) - which provides resources and guidance for the effective and efficient management of backlogs of sexual assault kits (SAKs) not yet tested for evidence - focuses on Y-STR testing for male DNA foreign to the victim when traditional, autonomic short tandem repeat (STR) testing fails to produce identifying DNA.
In traditional STR testing, male DNA may be masked or in competition with excess amounts of female DNA. This may result in partial or no male STR DNA results. Y-STR testing, on the other hand, targets STR regions on the male Y chromosome that is passed through the paternal lineage (father to son). A Y-STR profile can be unmasked in the presence of female DNA. Y-STR testing is more sensitive than common biological fluid screening methods, such as traditional serology techniques and even some quantification methods that screen for total amounts of male and human DNA. Consequentially, Y-STR profiles have been developed in cases where seminal fluid or sperm were not detected by serology or when quantified male DNA is at a low level or even below the limit of detection. This means that Y-STR analysis can reinvigorate the investigation of cold cases that have screened negative or produced only the victim's DNA. This resource brief also discusses how newer STR commercial kits have incorporated at least one additional male-specific marker to assist with the detection of male DNA, determination of the number of contributors in a mixture, and guidance in the decision to proceed with Y-STR testing. 1 table and 11 references

Date Published: February 1, 2018