Yes, DNA is always accurate in solving crime, because a person has a unique set of DNA. A person cannot be mistaken for another one where DNA is concerned. It is the ultimate identifier. Where DNA is found at the scene, the jury can be sure that the person was at the scene.
There are cases where DNA is not always accurate in solving crime. This is when the persons involved in the crime were around the victim often, or were in a relationship with them, whether it was a friendship, romantic, or familial. Usually DNA is the best evidence in crime solving though.
I do not believe DNA is always accurate in solving a crime. There are many cases where DNA simply won't help. It also depends on where the DNA is found and how it is linked to the crime. For the cases where it is usable, I think it is generally accurate, but there are many cases where it can't be used.
DNA is always accurate because it can only come from one person, however it is not always accurate in solving crime. We have to find out why the DNA is there, how it got there, and so on and so forth. My DNA might be at a scene, but I was there an hour before and had nothing to do with it.