I was unable to find a "letter" from Missouri Governor Michael Parson about this case, but there is a press release from the Office of the Governor (url copied below). Here are some of the highlights of the Governor's statement to the press:
The Governor's Office offers the following summary of the crime: "Marcellus Williams murdered Felicia Gayle on August 11, 1998. He burglarized Ms. Gayle’s home, ambushed her as she left the shower, stabbed her 43 times and left the knife lodged in her neck."
Because of the bloody and brutal nature of the crime, the police were able to recover DNA evidence at the crime scene. However, as the Innocence Project observed, the DNA evidence that was left behind by the killer does not match Marcellus Williams. The perpetrator left a knife in the victim's neck, but the DNA recovered from the knife - which could have conclusively determined who killed the victim - was contaminated and destroyed by the state, as noted by the Innocence Project.
Yet, the governor's press release completely ignores these facts, and then proceeds to deliver an astonishing statement: "I also want to add how deeply disturbed we’ve been about how this case has been covered. Mr. Williams’ attorneys chose to muddy the waters about DNA evidence, claims of which Courts have repeatedly rejected. Yet, some media outlets and activist groups have continued such claims without so much of a mention of the judicial proceedings or an unbiased analysis of the facts."
DNA is proven science, and a true "unbiased analysis of the facts" would presumably include the critical details that (1) none of the DNA evidence recovered from the crime scene matched Williams, and (2) the murder weapon was mishandled by state investigators, thereby destroying potentially exculpatory evidence that could have exonerated Williams.
The other evidence cited by the Governor's Office is all circumstantial. Contrary to the Governor's assertions, the witnesses who testified against Williams were in fact incentivized with reward money, and they did not offer details of the crime that were unknown to the public through media reports.
In summary, there is no direct evidence connecting Marcellus Williams to the crime scene. The real murderer in this case is Missouri Governor Mike Parson.
https://governor.mo.gov/press-releases/archive/state-carry-o...
https://en.wikipedia.org/wiki/Murder_of_Felicia_Gayle