The nationally regarded consultants rejected a suggestion in a state prisons report last month that Castro's Sept. 3 hanging was not a suicide as originally believed.
The consultants' report released Tuesday says all available evidence, including a shrine-like display in Castro's cell and an increasing tone of frustration in his prison journal, point to suicide.
The 53-year-old Castro had just begun serving a life sentence plus 1,000 years for imprisoning and raping three women in his shuttered house for a decade.
Castro was found hanging in his cell from a sheet attached to a window hinge.
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