Of the original five from the Jellicoe Road, Jude is the only one who has no direct connection with the accident—he first encounters the group when he replants the poppy memorial to their families after the Cadets trample the original ones. Even though he was a late addition to the group, this act of kindness nonetheless makes Jude part of them. "They connected," Hannah's manuscript reads, "and somehow, the world of Webb and Fitz and Tate and Narnie became the focus of Jude's life" (2.85) whenever the Cadets came to Jellicoe.
While he considers the four survivors to be his "best friends" (2.90), Jude always sees himself as an outsider to the group and is frequently on the fringes of their dysfunction. When Narnie threatens to kill herself, for example, he "watched them fussing over her like they always seemed to" (12.92) rather than being directly involved with her. Later, when Fitz confesses to shooting Webb, he watches Narnie comfort Fitz and thinks, "He wished he had never met any of them" (19.71). So, you know, he loves them—and keeps his distance, too.
Jude's status as an outsider seems to continue into adulthood, even after he and Narnie begin a romantic relationship: "She'd look at me and I'd know what she was thinking," he tells Taylor. "That she wished I were her brother or Fitz or Tate" (24.208). It's almost like he feels guilty for surviving the ordeal of losing Webb—with Tate gone and Fitz and Webb dead, he thinks Hannah sees it as unfair that Jude's there instead of any of the others who were together for the accident. Of course, as Taylor tells him later, this isn't what Hannah really thinks. Still, though, Jude always feels separate from the rest of his friends due to his absence at the scene of the wreck.
Reading Hannah's manuscript, we get to know Jude as a young man drawn to the free-spiritedness of the rest of the group. The stark, sullen military commander who enters Taylor's life as simply "The Brigadier," though, is far different. The Brigadier's imposing presence is so intimidating that Jessa McKenzie is convinced that he's the serial killer who's been terrorizing their region. As a result, we aren't totally sure what to think of him for most of the book, especially after Taylor breaks into his tent and finds the newspaper article accusing him of kidnapping.
At the end of the day, though, Jude's cold personality comes more from his position as a military commander, as well as the memories tied to Jellicoe, than any ill intent, and he most certainly isn't a serial killer. In fact, he deeply loves Taylor, which is why he came after her during her attempted exodus with Jonah Griggs—and his love for her goes back to the time she lived with him and Hannah.
Taylor realizes this when Jude catches up to Taylor after she runs off in shock over the news that her mother is dying. As he comforts her, she states:
He holds onto me in a way that Hannah never has. I feel his relief, like he hasn't held someone in a long, long time. And he's wanted to. (24.130)
Despite being an outsider from the original group on the Jellicoe Road, despite his hardened demeanor, Jude Scanlon is a loving, deeply emotional person who bears his own scars from the Schroeders' and Markhams' suffering.