As a boy, one day when walking home from school, a couple of cars drove into Julian's neighborhood, he got caught in a crossfire when a stray bullet hit him, relegating him to a wheelchair. Despite that, his intelligence and willpower kept him going. He is married to Mara and they have two children - Ronnie and Lucy.
In the pilot episode, when the Viper is being tested out, Julian is conducting it from behind a computer. However, after yet sixth test-driver, Madison, crashes the Viper, Julian is annoyed. Later, Julian is visited by Councilman Strand and Commander Delia Thorne, who are quite annoyed that Julian is not able to find a suitable driver for the Viper.
Eventually, after a police chase, an Outfit driver, Michael Payton, has his memory erased by Strand and Thorne by a chip installed. Later, when Julian is at the breakfast table with his family, he is summoned to meet Strand and Thorne, who inform him that they have found a driver for his car - Joe Astor, a "transfer from Chicago, who was recently involved in an accident and has amnesia". Julian is none happier, asking "You expect some banged-up amnesiac to drive my car?" However, he is told that either Joe becomes the driver, or the Viper project gets scrapped. Julian agrees to give Joe a try, who proves to be the perfect candidate.After Joe gets kidnapped by his old team, the Highwaymen, and is told to hijack the Viper and bring it to them, Julian convinces him not to, despite Joe being angry at being brainwashed; telling him that he was given a second chance, as Michael Payton with his criminal lifestyle would not have been likely to survive long, and sooner or later would have died in prison, on a highway or in some Outfit double-cross. This eventually inspires Joe to continue on.After the Outfit bribes Strand to scrap the Viper project and destroy the car, Julian is told by Thorne that he will be moved back to Research Operations with a raise. Realizing that the Outfit is behind this, Julian angrily resigns. Meanwhile, Joe has stolen the Viper and hidden it in Julian's garage. Joe and Julian then go out to take out the Highwaymen as they prepare to free one of their own, Nichols, who had been captured. Julian is seen driving the car, controlling the accelerator by computer, while steering the car by himself.
Julian stays with the Viper team (himself, Joe and Frankie) throughout the season, serving as the team's mechanic, and a quasi-father figure to Joe. However, after he had left MetroPol, he would run into some financial troubles. He plans to set up a research and development company so that he would have a legitimate front and a steady income, but at first, his loan application is declined. However, he would eventually start up the company, named Wilkes Technologies. Later, he would take a job at Washington, D.C. Julian's car in the original series was a 1992 Dodge EPIC minivan, a concept car.
In Season 4's opener, Julian makes a comeback, credited as "Special Guest Star", having just finished designing a second Defender for MetroPol, this time based on a Viper GTS Coupe. He is now seen walking normally, albeit using a cane. As explained by Frankie (and himself), he has a new bio-mechanical device he created, that uses a morphing technology, mimicking the electro-chemical reactions in nerve tissues, implanted in his spine to support his shattered discs, allowing him to walk again. When he is told by corrupt FBI Agent Harper that the Viper will be delivered to Metro City in a convoy with also a decoy car present, and he will be driving the decoy, he doesn't like the arrangement and makes a call, asking someone to deliver the real Viper instead.
This someone turns out to be Joe, who is now back in Metro City after three years. When Julian is travelling in the truck carrying the decoy Viper, the convoy is hijacked and he gets taken hostage. Over the course he finds out that the hijackers were aware of the real Viper's capabilities, and keep him as a hostage, threatening to kill him unless the real Viper is delivered.
After Joe, alongside the project's MetroPol liaison, Detective Cameron Westlake, rescues Julian (and Agent Sherman Catlett, Harper's partner who was also kidnapped later on), Julian, Joe and Frankie are seen in Catlett's office. Frankie mentions that he's happy to have all three of them back together, but Julian informs him that NASA has offered him a job he couldn't refuse, as he had "always wondered what it would feel like to be weightless". When Joe also says that his job is done, Julian tells him that he had taken the liberty of talking to the FBI to get Joe reassigned to the team as the driver, just as Catlett and Westlake walk in. He also compliments Westlake that not another MetroPol detective can touch her arrest record, "even if you did blow up my car". Joe reluctantly accepts.
In the season, Julian would make two more cameo appearances.