Updated: Dec 16, 2018
The S.C. Supreme Court recently came out with a case dealing with admitting evidence of a defendant's suicide attempt as evidence of guilt. The defendant was charged with Criminal Sexual Conduct and while in jail for the charges, he attempted to hang himself with his bed sheets. The State put up a jail guard as a witness and also introduced photos of the incident to show a guilty conscience. The defendant maintains that this evidence was not relevant (401) and that its prejudicial effect outweighed its probative value (403).
The Court acknowledged that evidence of a defendant's guilt may usually be admitted (e.g., witness intimidation), however, a suicide attempt is much more complex and needs its own standard for admission:
The new standard set out by the Court, requires that the State establish "a clear and unmistakable nexus linking the suicide attempt to a guilty conscience derivative of the offense for which the defendant is on trial." Id.
Also note the last sentence: "...suicide-attempt evidence will rarely be admitted." Id.