Under what circumstance can a jury compare signatures?

A jury can compare signatures specifically when they are comparing a specimen with a disputed signature. This is essential because the jurors need to utilize their observations to determine the authenticity or validity of the signatures involved in a case.

In this context, comparing a known signature (the specimen) against a contested signature allows the jury to visually assess similarities and differences. This comparison is rooted in the jurors' ability to use common experience and observation skills, which is especially relevant when authenticity or forgery is in question.

The other circumstances mentioned in the incorrect options lack the direct relevance needed for the jury's task of verifying signatures. For instance, if documents are typewritten, it doesn't inherently provide any framework for signature comparison. Likewise, while expert analysis is valuable, it doesn't negate the jury's role in evaluating evidence themselves. Suspecting forgery may lead to a need for signature comparison, but it’s the act of comparing a known specimen with the disputed signature that is specifically sanctioned for the jury to act upon.