That's enough for a juror to say "not guilty". Any juror should say "guilty" only if they are certain that the defendant is guilty. How certain? Good question, but even 0.5% doubt is enough for me.
5% is the benefit of the doubt, not reasonable doubt.
It is saying it is not impossible for the accused to be innocent. But when is it impossible ? Unless the accused admits guilt & knows things only the criminal would know.
Even in today's DNA society, defence lawyers always claim the DNA has been contaminated.