Left to stage or mock could certainly be a type of signature.

Zodiak sent law enforcement and local newspapers messages in code. They were to mock and taunt and were also an aspect of his signature.

Pubic hairs at the scene of a sexual assault are common--not unique.

Now, if the pubic hairs were left in clumps in the palm of the victims hand--and that would be every victim--they could be seen as 'signature.'

One pubic hair found on a blanket and one found on the toe of another victim do not constitute signature since both most likely 'happened' during the course of the assaults.

Rainsong