The Lincoln Lawyer features several "side cases" from the first book in Michael Connelly's series of the same name. Netflix's The Lincoln Lawyer is primarily based on book two in the series, The Brass Verdict. However, several of the secondary cases featured on The Lincoln Lawyer are drawn from the first book in Connelly's series (also named The Lincoln Lawyer).
The primary case in Netflix's The Lincoln Lawyer is a double homicide allegedly committed by tech mogul Trevor Elliott. Like most of the show, the case is drawn from The Brass Verdict, with minor changes. In The Brass Verdict, the accused murderer is named Walter Elliott, and his fortune derives from movies, not the tech industry. Despite several other slight changes and adjustments mostly made to update the Elliott case and surrounding circumstances, Netflix's The Lincoln Lawyer largely follows Connelly's books.
However, The Lincoln Lawyer series features additional cases throughout season 1 that supplement the Elliott case, and not all of them are from The Brass Verdict. The Lincoln Lawyer's titular protagonist, Mickey Haller, inherits the caseload of murdered star lawyer Jerry Vincent in The Lincoln Lawyer season 1, episode 1 and takes on his own batch of cases. Key cases from his past also make appearances on the show, most notably the murder trial of Jesus Menendez, an innocent man who was framed for and convicted of murder. These "side cases" that supplement the Elliott trial serve to illustrate Haller's skill as a lawyer, form important subplots that support the central mystery of The Lincoln Lawyer, and further develop Haller's character. Four of The Lincoln Lawyer's cases are from book one of Connelly's series.
Harold "Hard-Case" Casey
Harold "Hard-Case" Casey was a member of the Road Saints Motorcycle Club. Haller defended him on drug and firearms charges, including the possession of stolen firearms, cultivation, possession, and sale of marijuana, and distribution of crystal meth. In Netflix's The Lincoln Lawyer, Haller takes Casey's case to appease the Road Saints Motorcycle Club on behalf of his lead investigator Cisco. As a former member of the Road Saints, Cisco is in debt to them, and Haller attempts to repay it by assisting them, compromising his own integrity. Although Cisco attempts to end this, it's not before Haller successfully defends Casey despite Casey's guilt. However, Haller has inherited his father's philosophy that it's easier to defend a guilty man and win than to defend an innocent man and lose, as this isn't the case that keeps him up at night. That would be the Menendez case, which remains unresolved until The Lincoln Lawyer season 1's ending.
Sam Scales
In book one, Haller defends Sam Scales, a con man who uses disaster relief and internet fundraising scams to steal credit card numbers. Although he doesn't clear Scales's name, Haller secures him a shorter sentence along with five years of probation. In Netflix's The Lincoln Lawyer, Scales is similarly arrested for internet fraud, soliciting donations for cancer research on a fake website to scam well-meaning donors. Scales admits that he has no money to pay Haller but has computer skills and offers to lend them to Haller in lieu of payment. At first, Haller turns down the offer. However, the character Sam Scales appears later in the show to assist Haller with a case after Haller warns him that if he doesn't find a way to pay, his case will be delayed and he'll likely be charged with wire fraud by the FBI.
Gloria "Glory Days" Dayton
In The Lincoln Lawyer book one, Haller represents high-end prostitute Gloria Dayton, who goes by the name "Glory Days." In the books, Dayton is arrested for prostitution and narcotics possession. Dayton also plays a role in several of Haller's other cases in an undercover capacity. In the books, Dayton conceals information from Haller and shifts loyalties, aligning with a corrupt DEA agent. In Netflix's The Lincoln Lawyer, Dayton is never explicitly referred to as Haller's client, and she's portrayed as more ethically forthright. Her primary wrong is failing to appear to testify in support of Jesus Menendez, and she's justified in her decision as Gloria Dayton is blackmailed by corrupt detective Lankford. Unfortunately, she is the only person who could clear Menendez. Dayton was attacked by the person actually guilty of the murder Menendez was convicted of, and her testimony could exclude Menendez based on her description of her attacker.
Jesus Menendez
Jesus Menendez is the side case with the most screentime in Netflix's The Lincoln Lawyer adaptation. The case haunts Haller because he knows for a fact that Menendez is innocent, but after Dayton fails to appear as the key defense witness, Haller is unable to secure an acquittal for Menendez. In the book, Menendez is arrested for the murder of Martha Renteria. The evidence against Menendez is overwhelming and the death penalty is on the table. Haller believes Menendez's best option is to plead guilty, and he takes Haller's advice. In Connelly's books, Haller exonerates Menendez by identifying the real killer, while Dayton, originally blocked by cops in Netflix's adaptation, now provides evidence that clears Menendez. In addition, in the books, Menendez is unforgiving of Haller's errors, suing him for malpractice. In contrast, Menendez is grateful for Haller's continued commitment to his case in the Netflix adaptation. A key difference is that Haller has an unwinnable case in the streaming series. Dayton's failure to testify, engineered by corrupt law enforcement, are at fault, rather than Haller.
Netflix's The Lincoln Lawyer is an adaptation of an entire series of books, but it notably skips the first in the series. Arguably, this was a smart choice to avoid redundancy since there is already a popular movie focused on book one. However, each book in the series builds on seeds of cases planted in previous books. Characters like Sam Scales and Gloria Dayton appear in later books, and their appearance in season 1 hints at future storylines and potential plot points for The Lincoln Lawyer season 2. Not only did it make sense to include select cases from book one in a season based on book two, it was necessary.