Summary of People v. Collins, 438 P.2d 33 (1968)
Facts: An elderly lady was shoved down and robbed of her purse by a person unknown or seen by the victim. When she looked up she saw a young lady running away. A nearby witness saw a woman run out of the alley and enter a yellow car. As it turned around he saw a Black male wearing a mustache and beard. He was uncertain of the man’s identity at the police lineup shortly afterward when Df was beardless. Prosecution called a math teacher to establish that there was an overwhelming probability that the crime was committed by the Df. He testified that there was a 1 in 12 million chance that the Dfs were innocent.
Issue: Whether evidence of mathematical probability has been properly introduced and used by the prosecution in a criminal case?
Holding: admission, over objection, of testimony of college mathematics instructor pertaining to mathematical theory of probability of persons with defendants’ distinctive characteristics having committed robbery, without adequate evidentiary foundation or adequate proof of statistical independence, and without furnishing any guidance to jury on crucial issue as to which, of admittedly few couples matching defendants’ characteristics, was guilty of committing robbery involved, constituted prejudicial error, especially in view of closeness of case.
Procedure: Obj were timely made to the math testimony, and tr. ct denied motion to strike testimony was only used to illustrate, Jury found Df guilty of second degree robbery. Reversed.
Rule: Introduction of evidence related to mathematical probability statistics require an adequate foundation in evidence and adequate proof of statistical independence.
Rationale: The record is devoid of any evidence relating to any of the six individual probability factors used. The prosecutor himself suggested what the various probabilities should be and these became the basis of the witness’ testimony. A foundation for the admissibility of the witness’ testimony was never even attempted to be laid out, let alone established.
State v. Sneed, “mathematical odds are not admissible as evidence to identify a Df in a criminal proceeding so long as the odds are based on estimates, the validity of which have never been demonstrated." Id at 862.
No proof was presented that the characteristics selected were mutually independent, even though the witness acknowledged that such condition was essential to the proper application of the “product rule" or “multiplication rule." The technique used by the prosecution could only lead to wild conjecture w/o demonstrated relevancy to the issues presented.
The objective measurement of the likelihood of a random couple possessing the characteristics allegedly distinguishing the robbers, was gravely misguided. No mathematical equation can prove beyond a reasonable doubt 1) that the guilty couple in fact possessed the characteristics described by the witnesses, or 2) that only one couple possessing those characteristics could be found in the entire LA area. The computation could only factor the probability of a random couple sharing the characteristics, not the characteristics of the actual guilty couple.
The jurors were undoubtedly impressed by the mystique of the mathematical demonstration but were unable to assess its relevancy or value.