Based on this demonstration, it seems that you can insert just about anything into a photograph, a video, or any other computer-generated image. And you can do it very inexpensively, and very quickly, unlike the old photo retouching process. In other words, soon you won't be able to believe your eyes. This has some troubling implications for trial evidence. Presumably, any time you can get a witness to testify that the picture offered in evidence resembles his recollection of the way things were at the time the picture was taken, then the picture comes in as evidence and goes to the factfinder, typically a jury. The only way a jury or a judge could evaluate the picture's accuracy is by trying to assess whether the witness was telling the truth.
I'm certainly not comfortable with that standard.