Often conscious memories are sketchy or even nonexistent. Hypnosis is often cited as a means of gathering legal evidence. Strictly speaking this is not true. Information from a regressed subject is sometimes used in the context of other evidence, but it is not itself evidence. A hypnotized subject's recollection of the license number of a car is worthless as evidence unless the actual car can be found and determined to have possibly been at the scene.
Hypnosis can be useful to gain access to the memories of someone suffering from traumatic amnesia.
But only if those memories receive other, independent support do they obtain the weight of evidence. The police find such a car owned by such a driver. Impact marks confirm their suspicions and the young man is arrested. The evidence is not testimony given under hypnosis, it is the hard facts obtained as a result of that testimony. But the regressed testimony of UFO witnesses cannot currently be confirmed by hard facts.