Waterbury, VT - 07/15/2015 The Federal Bureau of Investigation (FBI) Crime Laboratory has recently issued a bulletin to National DNA Index System (NDIS) participating laboratories advising them that it had identified errors in the FBI Short Tandem Repeat (STR) population database published in 1999 and 2001, and has subsequently provided amended data correcting these errors. The allele frequencies cited in these publications have been used by many forensic laboratories throughout the country for calculating DNA match statistics since 1999. The Vermont Forensic Laboratory (VFL) is one of the many laboratories that had utilized the published data for reporting DNA match estimation statistics since beginning STR DNA typing.
The errors were determined to be due to clerical mistakes during transcription and to limitation of older technology and software. Empirical studies conducted by the FBI, as well as additional laboratories, have shown that the difference in probabilities calculated with the original data compared to that of the amended data is nominal.
The VFL has taken immediate steps to address the issues identified. The availability of the 1999 FBI STR population data was suspended by the VFL on June 1, 2015. Between November 2014 and June 2015, the VFL has primarily utilized the 2013 NIST population database, as such it is unlikely that cases processed and reported after November 2014 are affected. The VFL has evaluated differences between the 1999 FBI population data and the amended 2015 FBI population data. Any statistical differences observed were minor and are consistent with the observances outlined by the FBI (within a factor of two).
Although the number of cases affected by these errors is likely significant, the statistical impact is not. However, statistical calculations for any affected case will be recalculated upon request.
For any questions regarding the notification received by the FBI, impact on previous DNA cases analyzed by the VFL, or the steps taken by our laboratory, please contact the Biology Section Supervisor, Joy Mapp, at 241-5286 or joy.mapp@vermont.gov.
An erratum was published in the July 2015 issue of the Journal of Forensic Sciences which contains the data showing the minimal effect of these errors.