Documents are very important elements of any court case. Not all evidences are in the form of testimonies; in fact, some cases have been lots and won by virtue of written documents. As far as presenting evidence in a criminal case is concerned, originals must be presented as much as possible.
However, if originals cannot be used for some reason, the copies must be certified as original by the appropriate agency authorized to certify them.
It is also important to mention that all documents that will be presented as evidence in a criminal case be given to the defense team beforehand so that the defense team is given the chance to challenge or rebut its contents.