(covers information from several alternate timelines)
Robau's death
A life sign, bio-sign, or biosignature is a signal or collection of signals given off by a lifeform that indicates that it is currently alive, or functional. They are unique to a species. Upon approaching another starship or a planet for which they had limited intelligence, starships usually performed a scan for life signs. This information became part of the bridge crew's determination as to whether to board the ship, send a landing party, or carry out any other action. By the 24th century, Starfleet sensors were sensitive enough to discern an individual's identity based on their biosignature. (Star Trek: Insurrection)
In 2152, the crew of the Enterprise managed to isolate Captain Archer's biosignature, confirming that he had not become a casualty of a conflict between Andorians and Vulcans on the surface of a contested planet. (ENT: "Cease Fire")
In 2154, Shran's crew was able to locate Ambassador Soval aboard Enterprise by isolating Soval's biosignature for the purpose of abducting and torturing him for information on Vulcan fleet deployments. (ENT: "Kir'Shara")
Later that year, the biosignature of a prisoner in Enterprise's sickbay revealed him to be Klingon, a fact which surprised the crew, as the augment virus had altered his outward appearance to resemble a Human. (ENT: "Affliction")
The USS Kelvin was designed to track its crew member's life signs. When Captain Richard Robau was murdered in 2233 of an alternate reality, the computer signaled his termination. (Star Trek)
The USS Enterprise also monitored life signs of crew in environmental suits undergoing space dives. (Star Trek; Star Trek Into Darkness)
Dr. Juliana Tainer was a Soong-type android that was designed to give off Human life signs. (TNG: "Inheritance")
In 2372, a subspace divergence field perfectly duplicated every particle of matter aboard the USS Voyager, a fact which was revealed to the crew when they realized that all of their sensor readings had doubled the moment they encountered the field, including mass, energy output, and biosignatures. (VOY: "Deadlock")
Later that year, Ensign Harry Kim, Voyager's chief of operations, was able to detect three extremely faint biosignatures 2.3 kilometers beneath the surface of a Kohl settlement, revealing the presence of a group of aliens in suspended animation. (VOY: "The Thaw")
In 2375, Lieutenant Daniels, the Enterprise-E's tactical officer, detected Captain Picard's biosignature aboard the Son'a collector. This allowed the Enterprise to beam Picard off of the collector moments before it exploded. (Star Trek: Insurrection)
In 2376, while attempting to salvage an ion distributor from the recently discovered Ares IV, Seven of Nine instructed Lieutenant Torres to obtain a transporter lock on both her biosignature and combadge, which she had placed on the corpse of Lieutenant John Kelly, allowing Torres to retrieve both Seven and Kelly at the same time. (VOY: "One Small Step")
Later that year, Seven was able to alter her own biosignature in a successful attempt to prevent the Voyager crew from obtaining a transporter lock on her, after she stole a shuttlecraft while experiencing paranoid delusions, believing that the crew had been conspiring against her. (VOY: "The Voyager Conspiracy")
Later in 2376, after crewman William Telfer was abducted by a dark matter lifeform, Crewman Tal Celes frantically attempted to locate Telfer's biosignature, with no success. (VOY: "Good Shepherd")
The next year, Ensign Kim managed to isolate the biosignatures of an away team which had successfully infiltrated a Borg tactical cube, but was unable to beam them out until the cube's shields were deactivated. (VOY: "Unimatrix Zero, Part II")
Later that year, General Geral, an Annari, informed Captain Janeway that he had recently detected two Human biosignatures aboard a warship, belonging to the Kraylor, a species with which the Annari were at war, and subsequently escorted Voyager out of Annari space. (VOY: "Nightingale")