Let’s assume there is disagreement about the preventability of suicide, and there could be found ways to reduce its frequency.

http://www.johnhoward.ab.ca/PUB/C41.htm

The court is not the place to settle scientific controversy. More outside scientific data are needed. A court’s asserting otherwise violates the fair hearing portion of procedural due process rights of the defendant.

From the obverse of the coin, physical or other restraint of the suicidal patient in the absence of an involuntary commitment granted by a judge may violate the substantive due process rights of even a prisoner. The prison sentence has deprived the prisoner of his right to go outside the prison and do as he pleases. Fine. However, he was not sentenced to lose control over his own body. For example, the prisoner would be free to refuse medication for a cold or a cancer. No one could force an antibiotic down his throat. Why should he be forced to refrain from killing himself, and not harming anyone else, even if very mentally ill?