These are fractures to the heads of the metacarpals. Overkill id defined as excessive force or numerous fatal injuries. Suicide wounds tend to occur on accessible areas, which are often bared in order to have maximum effect, e.g. sleeves rolled up to permit the slashing of wrists. Generally, the instrument responsible is nearby. Although slashing is common, actual stab wounds are quite rare in suicides.
Accidental injuries tend to be single wound, occurring on any part of the body.
Usually, the instrument is present at the site.