As with any biometric, both the False Acceptance Rate (i.e. what is the chance that two samples of different individuals match) as well as the False Rejection Rate (i.e. what is the chance that two samples of the same individual do not match) are important.
However, in DNA studies, it seems most attention goes to the FAR. The FAR is important indeed: in court it is unacceptable that an innocent person would have a large chance to be convicted based on a DNA sample. However, the FRR is also important: it is unacceptable that a criminal walks because the DNA test falsely rejected the match.
It seems that "DNA has an extremely low false acceptance rate, but an uncertain false rejection rate." (source: Cyber Crime: Concepts, Methodologies, Tools and Applications)
Now, my question is: are there any studies that have investigated this FRR for DNA? What are the statistics on this? The 'Innocence project' mentions that some criminals have been exonerated based on a DNA test after their conviction. Are we sure that those exonerated criminials were indeed innocent, or were they just falsely rejected?