I refer you to the article "The Wound Profile & The Human Body: Damage Pattern Correlation" by Martin L. Fackler M.D., in Wound Ballistics Review Volume 1, Number 3, pp. 12-19. The conclusion states:
The bullet penetration depth comparison, as well as the similarity in bullet deformation and yaw patterns, between human soft tissue and 10% gelatin have proven to be consistent and reliable. Every time there appeared to be an inconsistency (the German7.62 NATO bullet for example) a good reason was found and when the exact circumstances were matched, the results matched. The cases reported here comprise but a small fraction of the documented comparisons which have established 10% ordnance gelatin as a valid tissue simulant.
Firstly you have a typo: the article is in WBR Volume 1, Number 4.
Before we go down that rabbit hole, let me state for the record what my position is on the use of gel testing:
1) It's the closest approximation we have for a medium that equates to a narrow band of human soft tissues being struck by a bullet in controlled circumstances.
2) It has the advantage of being an ethical, reproducible test that anyone can do with not too onerous preparation requirements.
3) It is ideal for comparing two different projectiles or loadings.
I'm on board with gel testing for the reasons above, but there are trajectories and circumstances that can't be replicated in gel...or if they were (because I haven't seen it yet) the type of replication required would entail losing the benefits listed in (1) and (2) above.
I have personally seen 38 Special and 9 mm projectiles deviated completely off course when they struck the fascia of the anterior abdominal wall of the investing fascia of the lateral thigh musculature. Try simulating that with ballistic gelatin.
I have also seen this kind of deflection, and more besides.
These results can be replicated in ordnance gelatin. Fackler showed that when the exact circumstances are replicated the results in ordnance gelatin are virtually the same.
This is where the issue is. How do you replicate the circumstances? I am not saying we should demand this replication because I don't think it is feasible but how do you replicate in gel, a 90 degree change in trajectory when bone has not been struck?
In the article referenced above, here's what I take issue with on page 13:
Since most shots in the human body traverse various tissues, we would expect the wound profiles to vary somewhat, depending on the tissues traversed. However, the only radical departure has been found to occur when the projectile strikes bone: this predictably deforms the bullet more than soft tissue, reducing its overall penetration depth, and sometimes altering the angle of the projectile's course. Shots traversing only soft tissues in humans have shown damage patterns of remarkably close approximation to the wound profiles. (emphasis added by me)
The thing is, it isn't just bone where we see remarkable trajectory changes. I've seen a bullet do a 90 degree angle through an abdomen where no bone was struck. I went with the patient to theatre and saw the injuries for myself. That case is on LinkedIn, use this QR code so you don't have to join up or login:
https://www.linkedin.com/pulse/ptlgc-case-132-brandon-bertolli
In other cases I have seen, there has been deflection of the projectile, such that it has ended up between two tissue planes. What I suspect is going on in those cases is the bullet is encountering a tissue interface at an oblique angle in a manner that makes it susceptible to deflection. I also suspect it is more likely to happen in the second half of the trajectory where the bullet's velocity is less.
In the IWBA article, several cases are discussed where an actual wound did not match what the primary investigator was expecting, either because of impact velocity changes or because of differences between the construction of the case bullet versus the one used to construct the gel profile. I don't have any argument against that, it is obvious.
The same applies to cases where the ammunition has been recognised because it breaks into components that are recognisable radiologically.
I have also seen several cases where the retrieved projectile in a real shooting case has matched samples that I have in my collection.
I X-rayed a fellow who had an ND with a .45 Ranger SXT (marketed as Black Talon) whilst seated in a vehicle. The round went through his thigh, missing his jewels by only a narrow margin and then continued on through the seat. He had a very nasty wound but luckily no vascular injury. All he had was three or four small metallic specks on X-ray. He was patched up and sent home the same day.
The next day he came in and showed me the bullet. It was expanded like it had been fired in ballistic gel. He had recovered it under the car seat.
Here's a cropped portion of the radiograph from that case:
Then there was another case where one barb from another Ranger SXT (marketed as Black Talon) hooked on the ilium in a pelvis shot, causing a core-jacket separation. Here's the radiograph, look how the barb has been splayed back upon passing through the ilium:
It is obvious that bone makes a big difference! I can't see how that case can be replicated in gel: it might be possible, but not feasible. It would take a large number of shots with a lot of experimentation of what bone or other material to place in the path of the bullet to achieve that pattern of damage to the bullet (let alone the patient!). Just to achieve a similar bullet fragmentation pattern in gel would not be feasible in my opinion.
One area where the article is wanting is to do with penetration distances as estimated in comparisons between gel and what is seen on a radiograph. In the gel you can dissect the wound path and measure it, but on the radiographs you have some pitfalls:
1) Scale. What method have they used to make sure that photographs of profiles in gel (such as in the Croy case referenced in the article) are at the same scale as what the radiographs show? It is not an easy thing to do because the radiograph has to be taken with certain prospective controls such as having the wound profile parallel to the image receptor (in their case it would have been film since this was a few years back) and also there would have to be controls in place to work out what the magnification of the resultant radiograph was, so that the image could be manipulated or post processed to best match the gel photo. It is very difficult to do!
2) The trajectory may not be straight (even if the person was shot in the anatomical position, standing stationary).
3) The trajectory as applies to the victim may not be comparable to the radiological trajectory as plotted in the hospital. This means he was X-rayed in a different position, compared to the position he was in, when shot.
I have an example of this phenomenon, which I described in one of my cases here:
https://www.linkedin.com/pulse/ptlgc-case-120-brandon-bertolli
In that case the supine trajectory doesn't make sense because the victim was shot whilst seated and he was X-rayed supine (lying down).
Then you have projectional differences between how bullet fragments and entry and exit markers are viewed on radiographs versus the "flat" panoramic photograph of a gel block. It isn't a criticism of gel testing, it is something I point out as a difficulty when comparing the two imaging modalities for the purposes of making penetration distance and trajectory comparisons. Indeed it may well be that the actual penetration distances quoted in the article may not have been so disparate in the Croy case. Well... this could go in the favour of the gel approximations or against them. They quoted a disparity of 1" in the article. It is difficult to place any stock in that because no methods for aligning the two modalities have been mentioned.
As far as tissue interfaces are concerned, look what they say on page 16:
Rick then sent me five of the unfired bullets (identical to the two recovered from the body) and I fired them into 10% gelatin. They penetrated 25, 24, 33, 26, and 28 inches (averaging 27.2 inches) and none of the bullets deformed at all. The reason for the difference in penetration depths in the gelatin could be seen in their yaw pattern, the first two yawed early in their path and the latter three showed minimum yaw. In addition, the first two bullets passed through a rib near the end of their tissue path (probably the equivalent of a few inches of soft tissue
penetration.) The bullets in the body passed through many interfaces between one tissue and another, this usually causes more yaw than passage through a homogeneous tissue simulant. All factors considered, the gelatin and tissue penetration depths compare well. (Emphasis is mine)
Well yes, it makes a difference! it is one of the reasons why outliers in the gel profiles versus wounds from real shootings are seen.
Also...there is a certain bias in how these cases are presented in the article. The cases are selected from a pool of data where the authors purport that the profiles as seen in real life are close approximations to what is seen in gel.
If a person was to read that article they might be under the false impression that no outlying cases exist. Well they do exist, because we see them in real injuries.
That is the main point I am trying to make here. It's not that I don't put any faith in gel testing, it's that I acknowledge the limited utility of it in approximating human tissues in certain circumstances.