The StrategyPage has a short article on the backlog facing the FBI in analyzing DNA samples - 40,000 samples in the que with a work-off rate of 4 samples per week! Automation will reportedly improve the work-off rate to 200 samples per week.
One data point that would be useful in getting a fuller picture would be the rate that new samples are being added to the que. If anyone has any information on that, please post it in the comments.
The article also gives a brief history of biometrics, starting with appearance (visual) and going through fingerprints (first recognized as unique 4 centuries ago!) and others until the recent methods of gait and DNA.