The former Sangamon County deputy is charged with shooting and killing Sonya Massey in her home.
Prosecutors said this case is clear as day. Former Deputy Grayson went into Massey's home, when she called for help, and unlawfully shot and killed her.
The defense, however, says Grayson feared for his life, when she would not listen to police commands.
Opening statements began in the high-profile murder trial that will largely center around police body-worn camera footage.
The former Sangamon County deputy is charged with killing the 36-year-old Black mother of two in July of last year.
Right off the bat, the state dismissed two lesser charges against the former deputy this week to focus solely on three counts of first-degree murder.
Grayson, pleading not guilty, said he acted in self-defense, because he thought Massey was going to throw a pot of boiling hot water on him.
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Day one of the trial wrapped up Wednesday afternoon following testimony.
A deputy who was with Grayson, Dawson Farley, testified that he did not believe that Massey was a threat.
Initially, Massey called 911 for help over a suspected prowler at her home near Springfield. She was known to have struggled with mental health. Grayson and another deputy never found anyone, but body camera video shows the situation escalating and Grayson fired three shots at Massey. Grayson was fired after that confrontation
Farley's body camera video recorded what transpired and was played in court. It shows Massey telling Grayson and Farley, "please don't hurt me" once she answered their knocks on her door. Once inside, Grayson and Massey go back and forth about a pot of water.
The video goes onto show Massey ducking a counter and briefly rising. That's when Grayson shoots her in the face.
The video elicited emotional reactions from Massey's mother and other relatives in the courtroom.
Earlier, Deputy Farley took the witness stand, saying that Massey did not appear to be a threat and wanted to "do right" by Massey by testifying for the prosecution in the case.
Grayson's body camera video was also shows his camera turned on after the shooting.
A review of the case by Illinois State Police found Grayson was unjustified in his use of deadly force.
Officials then revealed Grayson held six different law enforcement jobs over four years - along with two DUIs on his record before becoming an officer.
Governor JB Pritzker signed a new law, requiring stricter hiring practices for law enforcement, following Massey's death.
The murder trial is expected to last two weeks. If convicted, Grayson could face 45 years in prison.
Given the attention of the case, a judge also ordered the trial to be moved from Springfield, where the killing happened, to Peoria.
Testimony is expected to resume Thursday.