Just Mercy was written by Bryan Stevenson as a memoir. He tells the accounts of his experiences as a lawyer. Some of the stories he tells are about his actions in the courtroom. In particular, the actions are activist in nature, and he shows much more than the minimum level of respect for justice which is expected to be shown by most lawyers. The reader can tell that Stevenson does his job for much more than a paycheck, despite the fact that his efforts and actions to correct the system's biased ways are not particularly effective.

At trial, Stevenson seeks to appeal Walter McMillian's criminal conviction. He argues in his brief that the conviction should be overturned due to the miscarriage of justice that McMillian faced in the lower court. He cites examples such as untrustworthy witness testimony against his client, racial bias in the jury selection, prosecutorial misconduct, and what he perceived to be an improper act of the judge which overruled the jury's life sentence verdict, resulting in McMillian getting the death penalty.

Stevenson also strikes up a conversation with Myers, one of the witnesses who testifies against his client. Myers admits that he was not truthful in his testimony, and he also exposes the government's corruption in the system. Stevenson also exposes the biases that surround the criminal justice system. Based on the lack of justice that his client gets, Stevenson describes the criminal justice system as lacking compassion, effectiveness, and decency.

Ultimately, Stevenson's actions prove to be ineffective to get the result which he wants for his client and for the public. His client does not get treated fairly. The public is left with a system that is inherently biased and prejudiced. Stevenson's critiques of the system are supported and sensible.