The Chandra Levy verdict

I am probably stretching it, but here goes.

You may ask what's the recent verdict in the Chandra Levy case got to do with a diagnosis of schizophrenia?

Chandra Levy was an intern in Washington, D.C. who went out for a run one day in 2001 and never returned. Her body was discovered about a year later in a forested area off a jogging path.

On Monday Ingmar Guandique was convicted of her murder. Astonishingly, he was convicted despite the fact that there was no forensic evidence linking him to the crime, no murder weapon, no knowledge of what actually killed Chandra, no witnesses, and no confession on his part. Other lawyers declined the case because they felt it would be impossible to convict.
There was, however, testimony from a cell mate who claimed that Guandique "confessed" to the crime and from two female joggers who were molested by Guandique around the time that Chandra went missing.

It is astonishing that a conviction could be obtained based on lack of evidence and speculation. It looks like the jury based its verdict on what they would like to believe about the accused, and in doing so blithely overturned centuries of the common law principle of reasonable doubt. Other prosecution lawyers declined the case because they felt it was unwinnable.
A diagnosis of schizophrenia or other mental illness  is arrived at through similar leaps of faith. There is no scientific evidence that schizophrenia is a pathological disease, many people will not confess to being "sick," and yet they will be "convicted" anyway, based on their appearance and of acting outside of social norms.

Is it so astonishing that the Chandra Levy verdict is being heavily criticized for its lack of scientific evidence when those of us in the trenches see lack of scientific evidence guiding most of the legal and policy decisions governing mental health treatment?