Thanks! I thought I was in the criminal instructions. However, as you are doubtless aware, the standard instructions for criminal cases also prohibit speculation and require inferences to be based on evidence. RSBM, BBM:
E:03 PRESUMPTION OF INNOCENCE, BURDEN OF PROOF, AND REASONABLE DOUBT
"...
The burden of proof is upon the prosecution to prove to the satisfaction of the jury beyond a reasonable doubt the existence of all of the elements necessary to constitute the crime charged.
Reasonable doubt means a doubt based upon reason and common sense which arises from a fair and rational consideration of all of the evidence, or the lack of evidence, in the case. It
is a doubt which is not a vague, speculative or imaginary doubt, but such a doubt as would cause reasonable people to hesitate to act in matters of importance to themselves.
..."
D:11 INFERENCES—GENERAL
A permissible inference allows, but does not require, you to find a fact from proof of another fact or facts,
if that conclusion is justified by the evidence as a whole. It is entirely your decision to determine what weight shall be given the evidence.
..".
I am aware that the pattern jury instructions are sometimes modified by the judge after hearing from both parties. But these two would seem to be so fundamental as to require no amendment.
I would be interested to hear about a case in which speculation was allowed!