As an ensign, Lavelle shared quarters with his friend Taurik on board the Enterprise-D, something he was not always happy about. He was also the conn officer on the alpha shift. Besides Taurik, his circle of friends included Nurse Alyssa Ogawa, Ensign Sito Jaxa, and Ten Forward waiter Ben. The group had regular poker nights, sometimes including Ogawa's fiancé, Lieutenant Andrew Powell. Powell was one of the worst poker players that Lavelle had ever met.
Lavelle was career-oriented and driven and most wanted a promotion. In 2370, he was up for the operations officer position, in competition with Sito Jaxa. Although he was the obvious choice for the promotion, his uncertain relationship with his commanding officer William T. Riker somewhat got him off to a rough start. Lavelle was always nervous around him and Riker took the opportunity to criticize small issues, to Lavelle's general embarrassment. Lavelle's friends thought he was just imagining the situation, but Lavelle believed that Riker did not like him and had it in for him. Even though Lavelle tried to get on Riker's good side and had an immense amount of respect for him, Lavelle believed Riker to be uptight, once stating that Riker probably slept in his uniform.
Ben once encouraged Lavelle to introduce himself and get to know Riker. However, Lavelle's interaction with Riker was awkward and short-lived: on the basis of erroneous information from Ben, Lavelle had believed Riker to be from Canada, like his own grandfather, and struck up a conversation with Riker. But when it turned out that Riker was actually from Alaska, a much embarrassed Lavelle quickly retreated, regretting having once again said the wrong thing. Lavelle was sure that he would not get the promotion if it was up to Riker.
Riker saw these incidents as no more than attempts by Lavelle to ingratiate himself. However, Counselor Troi pointed out to him that he and Lavelle were a lot alike and that Riker should not hold Lavelle's inexperience with such matters against him. Troi's advice convinced Riker, who decided that he may have been too hard on Lavelle.
After Sito's disappearance during a secret mission, Lavelle was eventually promoted to the ops position and to the rank of lieutenant junior grade, although his success was bittersweet because it was accompanied by a certain amount of guilt. His friends told him that Sito would have been happy for him and that the best way to honor Sito's memory would be to excel in his new position. (TNG: "Lower Decks")
|Operations officers of the starships Enterprise|
|USS Enterprise-D:||Crusher • Data • Giusti • Gleason • Lavelle • Lopez • Mandel • Sito • T'Su • Wallace • Worf • Unnamed|
|USS Enterprise-E:||Armstrong • Data • Perim • Unnamed|
The character concept of Lavelle was devised by Ron Wilkerson and Jean Louise Matthias, who wrote the story of TNG: "Lower Decks" together. "They came up with the character to pair with Riker, a young hotshot," said René Echevarria, who wrote the episode's script. (Cinefantastique, Vol. 25/26, No. 6/1, p. 79)
Sam Lavelle's name came from two sources: a close friend of René Echevarria and Ron Wilkerson's Canadian Labrador Samwell. (Star Trek: The Next Generation Companion (2nd ed., p. 283)) It is unknown whether Lavelle's full given name is Samuel, as the Star Trek: Starship Creator bios written by Mike and Denise Okuda claim.
His name was spelled "Lauelle" in the first draft script.
The final draft script of "Lower Decks" describes Lavelle as being in his "early to mid-twenties" at the time of the episode. The script goes on to say, "Lavelle is bright, handsome and personable -- think of Riker twelve years ago."
Lavelle was played by actor Dan Gauthier. "He had, he has a 'young Riker' vibe," observed René Echevarria. "You know, that was definitely by design [....] He's very charming." Denise Okuda agreed, "Yeah, he's really very good." One element which she found "interesting" was that, in Lavelle's final scene, Gauthier can be seen doing what the Okudas referred to as "the Riker Maneuver," swinging one of his legs over a bar seat before sitting down. ("Lower Decks" audio commentary, TNG Season 7 Blu-ray special features)
In developing the characters for Star Trek: Lower Decks, Mike McMahan described all four leads in an 10 August 2020 TrekMovie.com interview as a combination of other Star Trek characters, parts of himself, and people in his life. Bradward Boimler was partially based on Lavelle, "a great Starfleet officer, but he's just so dedicated to trying to rank up and he's so careful about everything that he doesn't get to be Kirk." 
The game Starship Creator states that Lavelle was born in 2352, though this would make him only about eighteen at the time of "Lower Decks". This may indicate that he is precocious and further supports the belief that Starfleet entrance eligibility is not dependent on biological age but rather intelligence level and relative mental maturity. According to his biography, Lavelle was born in Tycho City, Luna to parents Rebecca and Irving Lavelle. He has a brother named Peter.
In "Heart of Darkness", a comic book of the Star Trek Unlimited series, Lavelle was mentioned as ascending to tactical officer and security chief of the USS Enterprise-E with the rank of full lieutenant.
In the novel series Star Trek: The Dominion War, Lavelle was serving with Taurik on the USS Aizawa after the outbreak of the Dominion War. The Pocket TNG novel Behind Enemy Lines mentioned that Lavelle and others from the Aizawa became prisoners of war of the Dominion and were taken to an internment camp in the Badlands, while the novel Tunnel Through the Stars depicted his return to the Federation and wartime romance with Ro Laren.
In an alternate timeline illustrated in the TNG Myriad Universes short story Brave New World, Lavelle achieved the rank of lieutenant and was serving as flight control officer on board the Enterprise-D by 2378. In that timeline, he was romantically involved with Sito Jaxa.