So far as I can find, SWGFAST does not recommend avoiding any but what SGTIT calls "traditional enhancement techniques." It does, as it should, call for preservation of original and working files and documentation such that the processes can be replicated and evaluated. SWGIT goes into considerable detail of the natures, benefits, and hazards of various enhancement, restoration, and compression processes. SWGIT also states:
Processed images are used for many purposes by the forensic science community. They can yield information not readily apparent in the original image, which can assist an expert in drawing a conclusion that might not otherwise be reached.
And they frankly include enhancement in processed images.
I think this accurately expresses the intent. Available techniques that enhance the value of evidence cannot be rejected simply because the software code is unavailable. One might also attack darkroom techniques used to produce images without an accompanying highly technical and product-specific explanation of the processes. As SWGIT notes, all of the techniques addressed as enhancement have roots in the darkroom silver processes. In general, imaging software merely provides a more efficient way to accomplish the same things. Some are direct analogues. The unsharp mask's odd name reflects the fact that it does exactly what we would did with a physical mask. It only seems nifty because not many photographers did it until they could do it digitally. We could do it step by step in a digital environment and indeed had to before it was reduced to a predefined process. I could create the mask and apply it digitally, but that would be pretty silly.
Similarly, the combining of bracketed exposures to display high dynamic range images dates to the 1850's (limited film response drove the effort) and notably from the 1930's. Some enhancements of course have no silver analogue, since they involve operations on pixels relative to other pixels. But it can be hard to make overall true statement about non-traditional techniques. Noise reduction, for instance. Actual noise doesn't occur in film. (Grain is something else.) But even digital noise or sensor dust spotting can be addressed with traditional methods with more or less trouble and effort, and a lot of what's done digitally is exactly what would be done in the darkroom. And while, admittedly, non-linear contrast controls, curve adjustment, is slicker in digital, something similar could be applied in the darkroom, if you wanted to make a heavy investment in time and experimentation. Some things - pattern noise and demoireing and halftone removal - would be beyond all but the most adept darkroom artist, who would probably go mad in the process.
The point is that, if the original image, working images, and documentation of the specific processes applied and the workflow are maintained, any advocate can fairly argue the toss. And latent print imaging is perhaps the most straightforward application. We are not often concerned with color rendition, and our images are normally captured under controlled conditions, and such things as blur reduction are not needed. And, since we are accustomed to dealing with distortions, we wouldn't often feel the need to do geometric adjustments, except to explain the distortion. These things are, of course, much bigger issues in some crime scene work. And for perspective, we don't feel obliged to come to court armed with knowledge of chemical interactions with particular substrates to defend against the argument that this or that detail is some kind of migration of developed matrix through the paper that only
looks like it's ridge.
We do have to be ready to talk about what was done and why it doesn't create or destroy. The digital operator should be trained and available to testify. (Especially important today, since that could well be a reasonable extension of the principle expressed in the recent SCOTUS ruling on lab analysts being available in person.) The reality is that our most likely task is to defend against an implication that "you could have done anything with Photoshop." But juries do readily recognize that digital enhancement is in routine forensic use. (They have probably been led to believe you can do legitimate miracles.) And you have SWGFAST, SWGIT, and publication of articles like that in the JFI to back you up. And the availability of code is really not an issue. In the unlikely event it was needed, expert testimony on the nature of the processes and what it can or can't do is readily available and applicable to whatever tool is used, PS, PSP, Gimp (including it and open-source plug-ins for which code is openly available), or whatever. But I will agree that no one should walk in with an HDR image product without being thoroughly familiar with how it works and with a decent prepared talk explaining it and without having prepared the attorney they're working with.