What must a lay witness have in order to express an opinion on a signature?

For a lay witness to express an opinion on a signature, they must have familiarity with the person's signature. This familiarity allows the witness to provide a non-expert opinion based on their personal observations and interactions with the individual whose signature is in question. The law recognizes that someone who has had regular interactions with a person may have acquired sufficient knowledge to identify and assess the authenticity of that person's signature.

This requirement does not necessitate expert training or qualifications in handwriting analysis, as a lay witness is allowed to offer opinions derived from their own experience and perceptions. The key factor is whether the witness has had adequate exposure to the signature in question to form a reliable opinion, rather than formal credentials or specialized training.