You don't specify, but presumably you mean a true confession.

It could also be used to generate a false confession. If the prosecutor says "We have proof you were there at the scene" and shows you some generated image, then you as an innocent person have to weigh the chances of the jury being fooled by the image (and even if it's not admissable in court, it may be enough to convince the investiging team that you are responsible and stop looking for the real perpetrator) and the expected sentences if you maintain your innocence vs "admitting" your guilt.

It could also narrow down the list of suspects. From there, additional investigation can find more evidence. Having access to big data can help this.

true, it cannot be used to "nail" a perp tho, just to help gain extra evidence.

Yup. In a court of law, the value as evidence is going to be weighted fairly low, even with expert testimony. It may be enough to get a warrant, or a piece in the process of deduction during the investigation phase.