In 2371 Commander Chakotay's bio-neural energy was displaced by trianic energy beings known as the Komar. Although he was pronounced brain-dead by USS Voyager's Emergency Medical Hologram, his disembodied consciousness remained intact, able to navigate and take control of other lifeforms. (VOY: "Cathexis")
It was possible to identify an individual through their bio-neural energy, as it formed a unique signature. In humans, such a signature was hard to fake due to naturally occurring variations that would enable a skilled physician to detect an artificially-generated signature.
In 2257 a Daedalus Project file, found by Ensign Sylvia Tilly, stored a bio-neural signature which both Tilly and Dr. Hugh Culber considered a 100% match for Michael Burnham. It was eventually discovered that the signature instead identified Burnham's mother, Dr. Gabrielle Burnham. Dr. Culber explained that biological similarities between mothers and daughters, particularly in mitochondrial DNA, explained the case of mistaken identity. (DIS: "The Red Angel", "Perpetual Infinity")