Is DNA as accurate as we think???

Those interested in following my eighth-graders' journey through It's Not Fair!, our justice unit, might like to take a look at the essay linked below.  Renzulli Learning has this description:

What is the likelihood that someone on trial for murder is innocent, if the odds are a billion to one against anyone else in the world sharing the DNA found at the crime scene? It's more likely than you might think, if you take all the odds into consideration!

http://www.tc3.edu/instruct/sbrown/stat/jury.htm