Margaret Schwartz, Ph.D. and Eric Buel, Ph.D.
State of Vermont Forensic Laboratory, Waterbury, VT

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Courtroom testimony regarding the probability of a match is fundamental to the DNA analysis process. Juries may have a difficult time evaluating statistics which employ numbers beyond reasonable comprehension. Often, concrete examples provide the link that assists juries to understand the statistical value of DNA analysis.

We have examined double first cousins in an attempt to present an example of the power of DNA analysis. In concept, it is easy to understand that the probability of a close relative of a suspect having the same DNA type is significant. If these closely related individuals can be distinguished and the magnitude of DNA variation demonstrated, then the statistics presented for unrelated individuals is more palatable. We present DQA1, PM and RFLP analysis data on eight double first cousins and their parents. The ability of these systems, singly and in combination, to distinguish closely related individuals will be discussed.