Twenty-nine

In early May, Vernon Davids and Pete Ragsdale spent four days in Washington, D.C., interviewing the FBI experts who had tested the physical evidence.  It was the defense's only chance to interview these witnesses before they testified at trial.  Frye, Jack Bachman, and Steve Thacker represented the prosecution.

William Gavin, the serologist and chief examiner on the case, said that he had used a spot-checking method in testing the bloodstains on clothes.  Therefore he could not say positively that a certain type of blood did not occur on a garment, only that he had not found it in the places he sampled.  This was especially important in the case of Zeigler's shirt and trousers, which seemed to show a preponderance of Type A blood, rather than his own Type O.

(Further, Type A blood contains A antigens, while O blood is identified by the absence of both A and B antigens.  Therefore, when A and O blood are mixed, even a relatively small proportion of A antigens will type the mixture as A blood.  A deeper subgrouping would likely have eliminated this ambiguity.)

Gavin suggested that the blood samples the OCSO had submitted were too slight to be subgrouped.  His explanation for the failure to subgroup did not satisfy Davids.  Not even the large "known" samples drawn from Tommy Zeigler and the four corpses had been subgrouped beyond a basic RH factory (Tommy Zeigler's blood was RH-negative; all the others were positive).  This seemed to imply that Gavin never intended to subgroup the evidence, however large or small the dry blood samples might have been.

Ruby Lee Ross, a fingerprint expert, told the visitors that she had identified Zeigler's palm print on one of the cabinet bags.  She said that she had photographed some partial prints on the .357 magnum, but that they contained too few points for positive identification.

And then, she said, she had burned the photographs of those partials.

Davids was aghast.  The prints might not have been valid for positive identification, but they could conceivably have shown a unique feature that eliminated Zeigler as the source of the prints.  And that would virtually exonerate him, since the prosecution maintained that he alone had fired all twenty-eight shots in the store.  But the evidence, whatever it showed, was now gone for-ever.

Davids asked why had she destroyed the photos.

She answered: because they were of no value for identification.1

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1    From a 1981 FBI handbook for police departments submitting material to the FBI Lab.  "All original evidence will be returned to contributing agency unless directed to make some other disposition by the contributing agency."