Your mistake is that you assume there is such a thing as definitive data. While I respect Dr. Roberts, his is but one voice in a field containing many and there is very little consensus within that field.
Dr. Roberts' work, along with others like Duncan MacPhearson, Shawn Dodson, and the FBI, is based heavily upon that of Dr. Martin Fackler. Unfortunately, many if not most of the "experts" whose opinions are based on the work of Dr. Fackler take his conclusions to logical extremes and fail to explain, or perhaps even understand, how and why Dr. Fackler came to those conclusions to begin with.
For example, many want to discount temporary cavitation, and by extension kinetic energy transfer, all together because Dr. Fackler said that it was an unreliable wounding mechanism at handgun velocities. What seems to be lost, however, is that just because something is unreliable that does not mean that it is non-existant.
The reason, according to Dr. Fackler, that temporary cavitation is unreliable with handguns is that many tissues in the human body are too elastic to be significantly damaged by the temporary cavitation produced by most common handgun cartridges. Dr. Fackler does, however, qualify that statment by noting that certain tissues (he uses liver tissue as an example) are very inelastic and can be damaged by handgun-level temporary cavity. Dr. Fackler has also done very little work with the more powerful handgun cartridges like .41 Magnum, .44 Magnum, and .454 Casull that generate much more kinetic energy and, with careful bullet selection, much larger temporary cavities than most common handgun cartridges do.
Another example is the almost pathological fear of bullets which fragment. Because Dr. Fackler generally admonishes against fragmenting handgun bullets, many seem to feel that anything less than 90% weight retention is completely unacceptable. What is lost is that the reason Dr. Fackler admonishes against fragmenting handgun bullets is because they typically display lackluster penetration. This is not, however, universally true as there are some bullets that can fragment significantly without sacrificing adequate penetration and, if the fragmentation occurs deep enough with large enough fragments, it can actually increase the bullet's wounding potential. An example of this is the semi-jacketed hollowpoints often found in revolver cartridges like .357 Magnum. A 125gr .357 Magnum SJHP will quite often shed is jacket in large shards while the lead core continues to penetrate 11-13" while retaining 60% or more of its weight.
