[9][10] In the late 1980s, an investigation conducted by the Dallas attorney general's office looked into the post-conviction outcomes of murder convicts whom Grigson had testified against.
[9] One of the most notable, at least after the fact, appearances of Grigson in court occurred in the 1977 case of Randall Dale Adams, who was accused of murdering police officer Robert W. Wood.
[16] In 1997, the Texas Court of Criminal Appeals overturned Cook's conviction on the grounds of prosecutorial and police misconduct, and he was freed after agreeing to plead no contest to a time-served sentence.
[18] His testimony helped prosecutors secure the death penalty, but Willingham's guilt has since been called into question due to modern fire science[19][20] and a witness recantation.
[25] Executed defendants whose cases Grigson testified in include Aaron Lee Fuller, Bernard Eugene Amos, David Lee Holland, David Wayne Stoker, Gayland Charles Bradford, Gerald Wayne Tigner, Gregory Lynn Summers, Hai Hai Vuong, Jack Wade Clark, James Edward Clayton, John Glenn Moody, John Russell Thompson, John Thomas Satterwhite, Mack Oran Hill, Michael Dewayne Johnson, Noble Mays Jr., Patrick Fitzgerald Rogers, Samuel Christopher Hawkins, Thomas Andy Barefoot, William Hamilton Little, and many more.
[6][8][27] The American Psychiatric Association stated that Grigson had violated the organization's ethics code by "arriving at a psychiatric diagnosis without first having examined the individuals in question and for indicating while testifying in court as an expert witness that he could predict with one hundred percent certainty that the individuals would engage in future violent acts".