Death penalty
The death penalty was the state-sanctioned execution of an individual or party, subsequent to some sort of legal process or custom. Typically – but not necessarily – applied as a punishment for serious crimes such as murder, it could also be the consequence for religious offense, affront to honor, or an act of political expediency. Justification for, and frequency of, the use of the death penalty varied widely throughout known space.

Pre-Federation 
Centuries before 2364, some of the countries of Earth, believing the death penalty a justifiable deterrent for criminality, practiced this most severe of punishments on those they deemed most threatening to society. Eventually, as criminal behavior was detected in its infancy in individuals and the individuals themselves were treated for their criminal tendencies, the death penalty lost its hold and eventually ceased as a practice. (; )

Execution was common practice in ancient times. In Q's recreation of Sherwood Forest, Maid Marian as portrayed by Vash was to be executed for her refusal to marry Guy of Gisbourne. However, Vash turned the tables by agreeing to marry him, so Jean-Luc Picard in his role as Robin Hood was to be executed instead after he was caught trying to rescue Vash/Marian. Then, when Q / the High Sheriff of Nottingham discovered Vash with a message to Picard's crew, the Merry Men, he declared, "Guards! Take this traitor away. It appears there's going to be a double execution." ()

A Human being burned at the stake could be seen in the resetting timestream. ()

In the 22nd century, the Vulcans had very few crimes punishable by death. Treason was one such crime. ()

In 2153, a group of Triannons seized control of  and their religious leader, Pri'Nam D'Jamat ruled that one of the crew of the ship must die for their transgressions against the Delphic Expanse spheres. Captain Jonathan Archer selected himself and convinced D'Jamat that the transporter was a device that was used to dispose of hazardous materials, but was also sometimes used for humane executions. He was thus able to escape by being transported to another part of the ship. ()

The Federation and the death penalty 
Compared to neighboring civilizations, the United Federation of Planets was unusually reluctant to codify or apply the death penalty, preferring incarceration and rehabilitation. ()

Some Federation worlds, per the respect of the UFP to local and independent customs, had laws of their own which put citizens to death. Such was the case on Ardana which, even though a member of the Federation, practiced not only the death penalty but torture as well. ()

In the 23rd century, General Order 7 was issued subsequent to the 's visit to Talos IV in 2254. By 2267, the penalty for Starfleet officers violating General Order 7 was death. However, in the only known instance of the order's violation, Starfleet declined to prosecute the officers involved. ()

In 2256, Vice Admiral Katrina Cornwell told the Klingon L'Rell that the Federation had no death penalty. () Later that year, upon Voq's assertion that Michael Burnham should have allowed him to die for attempting to murder her, Saru responded that even with the  "stranded in a cruel, anarchic world", no crime was heinous enough to warrant overriding Federation law. ()

In 2259 of the alternate reality, Admiral  ordered  to execute the mass murderer John Harrison from orbit. , , and  all found the notion dubious, so Kirk deferred to their judgement and arrested Harrison instead, eventually learning Marcus had ordered the hit to eliminate a conspiracy of which Harrison was the only loose end. ()

In 2269, while inhabiting the body of Captain James T. Kirk, Janice Lester attempted to have Kirk – who was at the time inhabiting her body – executed for mutiny, along with Spock, Dr. Leonard McCoy, and Montgomery Scott. Pavel Chekov protested that Starfleet expressedly prohibited the death penalty except for General Order 4. Lester's insistence on carrying out the executions turned the remainder of the Enterprise crew against her. She and Captain Kirk returned to their original bodies before Lester could carry out the death sentence. ()

By the 24th century, the death penalty was non-existent in the Federation. (; ) Nonetheless, during a tense moment, captain Kathryn Janeway claimed her senior staff might be hanged for mutiny. ()

On one occasion in 2372, 's chief of security Lieutenant Tuvok asked Captain Janeway to consider using the death penalty in the case of crewmember Lon Suder, who had murdered a member of the Voyager crew. Due to Voyager having been nearly seventy years from Federation territory, Tuvok, who was affected by a mind-meld with the violent Suder, saw execution as a possible alternative to keeping Suder confined indefinitely. However Captain Janeway firmly rebuffed this suggestion, and Suder was kept confined to his quarters until his death in 2373. ()

Notable exceptions

Trial by combat 
Ritualistic murder to satisfy individual or collective honor was one form of death penalty common to several Alpha Quadrant worlds. , Qo'noS, and Andoria all had provisions for settling some legal disputes by personal combat to the death. The Vulcan kal-if-fee; Klingon Mauk-to'Vor, blood oath, Rite of Succession, and Right of Vengeance; and Andorian ushaan all received legal sanction from their respective societies. Some of these rituals, however tolerated they might have been by planetary governments, were in violation of Starfleet regulations. ()  The Klingon rituals, in particular, became troublesome for the Federation because there were some Federation citizens – like Worf, Curzon, Jadzia, and Ezri Dax – who were also members of Klingon houses. The response of superior officers to the engagement in Klingon death-by-combat rituals was inconsistent. Although Picard and Sisko came down hard on Worf for engaging in the Right of Vengeance and the Mauk-to'Vor, respectively, Sisko, in agreement with Ross, later tacitly supported Worf's ritualistic murder of Gowron. (; ) However, this apparent change in attitude may have had less to do with Starfleet policy and more to do with stopping Gowron from continuing to sabotage the war effort for petty reasons.

Reassociation 
The Trill punishment for reassociation was an effective death penalty for symbionts. Because the state, in such cases, refused to allow a symbiont found guilty of reassociation to be further joined, the symbiont's life was prematurely terminated. ()

Other civilizations and the death penalty

Cardassian Union 
The totalitarian Cardassian Union embraced the death penalty as a means to foster popular belief in an efficient and secure government. Show trials where the verdicts were foregone conclusions were broadcast frequently. Starfleet Chief Miles O'Brien narrowly avoided a death sentence on Cardassia in 2370. ()

Gul Dukat stated in 2371 that he wished he had Elim Garak executed "years ago" for unspecified actions involving his father. ()

Benjamin Sisko forced Dukat to ensure that Thomas Riker was sentenced to life imprisonment instead of being executed. In exchange, Dukat would be given the 's sensor logs and Thomas would be convicted to appease Dukat's political masters. ()

Klingon Empire 
The Klingon Empire's ancient justice system was suborned by the rising power of the Klingon warrior class in the 22nd century. Death sentences were meted out liberally. However, the sentence was sometimes commuted into an indefinite period of life-threatening servitude. An criminal in the 22nd century was released from death row in order to be a test subject in a Klingon laboratory on Qu'Vat Colony. The criminal Grathon Tolar was on a Klingon death row prior to Benjamin Sisko arranging for Gowron to pardon him so that the criminal could work for Sisko. He indicated that the Klingons liked to taunt such prisoners by telling them daily that they would be executed the next day. Jonathan Archer, James T. Kirk, and Leonard McCoy all had their Klingon death sentences commuted to a "life sentence" of slave labor in the dilithium mines of Rura Penthe. Worf promised J'Dan that the Klingon High Council would put him to a slow death for his role in suspected sabotage of the dilithium chamber hatch of the . (; ; ; )

Romulan Star Empire 
The Romulan Star Empire showed little evidence of a court system, but the legal authority to warrant and execute death sentences appeared to have been widely distributed. In 2268, Commander Spock was held for espionage by a Romulan commander, who described his death sentence as "painful and unpleasant", and which would be carried out immediately after the charge was recorded. Spock asked for, and was granted, the Right of Statement before execution, a tradition he used as a filibuster until he could be retrieved. () 

In 2349, a Tasha Yar from an alternate timeline tried to escape from Romulus with her daughter, Sela. She was caught and later executed when Sela cried out upon realizing she was being taken from her father. ()

In 2371, a Tal Shiar operative destroyed a Flaxian ship in Bajoran space, declaring the incident a perfectly legal execution of an assassin "wanted for crimes against the Romulan Empire." ()

Q Continuum 
The Q Continuum had on rare occasions executed s for certain crimes. They believed that their society, like any other, must control its disruptive elements, and that an an execution, while undesirable, was on rare occasions necessary and warranted. The decision to proceed was only made after great deliberation by the entire Continuum, to avoid chaos and anarchy. "Collaborating with the enemy" was considered a crime punishable by death. ()

Non-aligned worlds 
The Bajoran Provisional Government may have been willing to use the death penalty against Cardassian war criminals. This was certainly part of Aamin Marritza's thinking when he attempted to impersonate Gul Darhe'el. Odo confirmed that the Bajorans would use the death penalty during a subspace conversation with Gul Dukat. ()

The same year, Neela, who planned to assassinate Vedek Bareil Antos, feared that she would be caught and then executed. Vedek Winn Adami, who planned this, tried to calm her down and told her that this should be so if the will of the Prophets. ()

As of 2267, the penalty for fraud on Deneb V was death. Guilty parties had the choice of death by electrocution, gas, phaser, or hanging among their options. () 

The Ferengi Alliance also practiced the death penalty, especially against labor activists. The preferred method of execution was bringing the condemned to the spire of the Tower of Commerce of Ferenginar and pushing them off. These were public executions, and children would bet on where the bodies would land. ()

On the homeworlds of the Gosis' species and the Skagaran colony planet, hanging was a legal form of punishment. (). 

On Argelius II, a law prescribing the ancient penalty for murder, death by slow torture, was not abolished until at least the 2260s, even though the Argelians had been, by that time, a peace-loving culture for two hundred years. In 2267, chief administrator Hengist contemplated using this punishment on Montgomery Scott should he have been found guilty of a murder that turned out to have actually been committed by an entity known as Redjac. ()

The planet of Eminiar VII replaced collateral damage of war with the death penalty by asking a computer to calculate what areas of their cities would have been damaged in a battle, had one actually happened. The law of the planet then required citizens to voluntarily submit themselves to a "sanitary" execution. While not a punishment for crime, it was an institutionalized death penalty. ()

Similarly– if on a smaller scale – the mediators of Rubicun III enforced the law by randomly selecting a zone to patrol. If a citizen disobeyed the law in that zone, he or she was given an injection of poison. By not knowing in advance the location of a forbidden zone, the citizens of this world were deterred from criminal behavior. ()

The government of Kaelon II practiced a 1,400-year-old tradition by which all citizens were required to have their lives terminated at the age of 60. ()

In the Gamma Quadrant, the Rakhari practiced capital punishment as of the 2360s, when Croden's entire family was put to death since he spoke out against the repressive policies of the government. ()

In the Delta Quadrant, anyone discovered deserting from the Talaxian Defense Forces was given the death penalty during the Talaxian-Haakonian War. ()

In Nygean society, the victims of a crime determined the offender's punishment, which could include the death penalty in cases of murder. ()

Baneans used to punish murder by lethal injection, but by 2371 a punishment based on the implantation of memory engrams had been developed instead. ()

In the early 24th century, the Enarans utilized public executions to silence dissidents. The execution post would be placed in town centers and violators were tied to the center post. When activated, the post and violator would be bathed in a purple glow. The process took only a few seconds, but caused extreme pain. The device left the corpses with very badly burnt skin. ()

The mirror universe 
The death penalty was commonplace in both the Terran Empire and the Klingon-Cardassian Alliance. Failure to follow the direct orders of  could result in an immediate execution being ordered by Starfleet Command, to be carried out by the next-in-command. () But as in the Klingon Empire of the "normal" universe, the death penalty was often independently initiated by a particular officer, and usually had the effect of advancing one's rank. Unlike the Klingons, however, mirror Starfleet (and, later, Klingon-Cardassian) officers would carry out the murder of superiors or subordinates not out of a genuine desire to protect the crew from inept leadership, () but merely as the instrument of personal advancement. Justification for such behavior was often couched in language that suggested fealty to the higher cause of "the Empire" or "the Alliance", but most officers who ordered the death of another independent of higher authority were usually committing an act of simple murder. As evidenced by the sudden ascendancy of Empress , the right to kill was established by the might to kill, rather than a formal provision of law. ()

Away from military politics, Terran and Klingon-Cardassian behavior towards civilians was equally brutal. Executions were commonly meted out as a means of providing incentive to comply. Civilians were killed merely because they had committed the crime of disobedience to the will of the representative of the Terran or Klingon/Cardassian authority, or sometimes for no other reason than the whims of said representative. Indeed, the Intendant  once even suggested random executions as a means of keeping workers motivated. (; )

Appendices

Background information 
At least two Federation members, founding members no less, practiced duels to the death: the Andorians through the Ushaan, and the Vulcans through Kal-if-fee.

During his argument with the M-5 multitronic unit, Captain Kirk said the penalty for murder was death. It is unclear whether Kirk was reflecting his own belief, exploiting the nature of M-5's Human template, or reflecting a truth of the 23rd century that wasn't evident in descriptions given of the 22nd and 24th century Earth. ()

External links 
 
 

de:Todesstrafe
Punishments
Death