Nichols grew up in a middle class household in Baltimore, Maryland, and attended Cardinal Gibbons School.
He later attended Kutztown University of Pennsylvania in Kutztown, Pennsylvania, from 1989 to 1990, where he played football and was known for having a "knack for trouble". Nichols dropped out of college and moved to Georgia in 1995, where he worked for Hewlett-Packard and later UPS.
Nichols was later arrested on multiple charges for the rape, kidnapping, and assault of a former girlfriend after discovering that she was dating a minister from the church that they both attended. The first attempt at a trial ended with a mistrial and a hung jury. While awaiting a second trial, friends and family members of Nichols expressed concern that he would attempt to escape and that Nichols had tried to formulate an escape plan with a friend.
On March 11, 2005 Nichols overpowered a sheriff's deputy while changing clothes, stealing her gun (Glock), and beating her into a coma. Reports stated that Nichols had previously attempted to sneak "shanks" into the courtroom via his shoes. Nichols then changed into civilian clothes originally intended for use during the trial and entered the courthouse, where he entered the chambers of Judge Rowland Barnes.
On his way to Barnes's chambers, Nichols encountered case managers Susan Christy and Gina Clarke Thomas as well as attorney David Allman, whom he held at gunpoint and demanded directions to Barnes's location. During this time Sergeant Grantley White entered the courtroom and attempted to disarm Nichols but failed, and was forced to handcuff the others. White managed to set off an alarm, which Nichols attempted to dispel, using White's radio. Nichols later progressed into the courtroom where he fatally shot Barnes, as well as court reporter Julie Ann Brandau. He later fatally shot Sergeant Hoyt Teasley while escaping from the courthouse. Nichols car-jacked several vehicles during his escape and was featured on America's Most Wanted during his manhunt.
A reward of $65,000 was announced for anyone that could give information leading to Nichols' arrest. Attempts to find Nichols were largely unsuccessful and it was reported that Nichols had attempted to kidnap a young woman as she was walking home from a gymnasium she regularly attended. Nichols fled after hearing the young woman call 911 after her boyfriend defended her from Nichols. Later that day, U.S. Immigration and Customs Enforcement (ICE) Agent David G. Wilhelm was shot dead in his home and several of his belongings, including his badge, a gun, and a pickup truck, were stolen. Nichols was believed to have been a suspect in the shooting death.
Police later received a 9-1-1 call from a young woman by the name of Ashley Smith, who stated that Nichols was at her Duluth, Georgia apartment. Law enforcement responded to the scene where Nichols surrendered himself to the authorities. Authorities recovered several stolen firearms and Agent Wilhelm's wallet. The stolen truck was discovered about two miles away from the apartment. Smith later reported to police that she had been approached by Nichols on March 12, who forced his way into her apartment, and held her hostage at gunpoint for seven hours. Once in the apartment, she supplied Nichols with methamphetamine, and she also read portions of The Purpose Driven Life to him. She also tried convincing him to turn himself in by telling Nichols about her husband's death and showing him a scar that she had received from a car wreck while under the influence of drugs. After she made him pancakes for breakfast, Nichols allowed Smith to leave to see her daughter, allowing her to call the police. Smith later received reward money for her assistance in Nichols's capture.
After his arrest, Nichols was taken to an FBI field office in Decatur, Georgia, and then to the Atlanta Police Station where he confessed on video, and detailed his crimes.
On May 5, 2005 Nichols was indicted by a Fulton County grand jury on 54 counts including murder, felony murder, kidnapping, armed robbery, aggravated assault, aggravated battery, theft, carjacking, and escape from authorities. Nichols initially pleaded not guilty, with his lawyers stating that they wanted to defend Nichols on the basis of mental health. Fulton County District Attorney Paul Howard announced he would seek the death penalty. Nichols became Georgia's most expensive defendant, with his case topping $3 million for the prosecution and defense combined.
The case was presided over by Superior Court Judge Hilton Fuller and was set to take place in July in the same courtroom in which the earlier murders had taken place. The trial was temporarily placed on hold in order to find new accommodation, as Superior Court Judge James Bodiford ruled that "fundamental fairness" made it necessary to move the trial to another location. While awaiting trial Nichols attempted to make another escape which did not progress past the planning stage, and Nichols was moved to DeKalb County jail in October 2006. The trial began on September 22, 2008 in the Atlanta Municipal Court, where Nichols pleaded not guilty by reason of insanity and his defense attempted to have the trial delayed. This was refused.
During the trial audio recordings of the murders were played, with the prosecution attempting to discredit Nichols's claims of mental instability. Witnesses were brought forward who testified that Nichols had not shown signs of mental illness during his rape trial. The prison guard who Nichols had attacked, was not able to testify at the trial, as the injuries she had sustained had left her with no memory of the event.
Nichols admitted to the shootings in a statement to the police, but claimed that the shooting of Wilhelm was due to the agent pointing a gun at him. Forensic evidence did not support this statement, instead showing that Wilhelm had been shot while kneeling and that he had other injuries, which indicated that Wilhelm was not holding a gun.
Nichols's defense argued that he was insane and should not be held accountable for his actions. The defense stated that he had previously shown signs of depression and suicidal ideations after breaking up with his girlfriend. An attorney who represented Nichols in his rape trial testified that Nichols had expressed belief that his ex-girlfriend would not testify against him and still loved him despite receiving injuries from the rape. Psychology experts were brought forward to testify that Nichols had had an abusive childhood and that his father's history of drug abuse led to Nichols abusing drugs in his adult life as well. The defense also provided college papers written by Nichols that expressed Nichols's belief that white people were involved in a conspiracy to eradicate the black race.
The jury deliberated for twelve hours, over two days, before finding Nichols guilty of all 54 counts, on November 7, 2008.
On December 13, 2008, Nichols was sentenced to multiple life sentences with no chance of parole. Bodiford handed down the maximum sentence on each of the charges, to run consecutively. Nichols was spared multiple death sentences when the jury failed to reach a unanimous decision, as required by Georgia law, to recommend the death penalty. Bodiford said, "If there was any more I could give you, I would." Nichols is incarcerated in Georgia Diagnostic and Classification State Prison.
Some family members of the victims filed civil lawsuits against Fulton County, Georgia. Judge Barnes' widow won a $5.2 million lawsuit. County commissioners agreed to pay $5 million to Julie Ann Brandau's daughter, Christina Scholte, who also sued.
David Oyelowo portrays Nichols in the 2015 biographical drama Captive.
Ashley Smith wrote a book about her ordeal with Nichols titled, “Unlikely Angel: The Untold Story of the Atlanta Hostage Hero”.