I know that crucifixions were usually done by tying the victim to the cross, but if I recall, there were exceptions made to this, of which Jesus is said to have been one - which I think is even noted in Bibilical accounts - while the two crucified with him were tied. But the evidence that these particular nails were used is pure speculation based on sketchy circumstances. And why would the Caiaphas keep them even to his grave to begin with?
Russian defense ministry: Plane sent to intercept U.S. plane near border on Friday (Reuters)
from the article: Experts question claims of crucifixion nails' discovery