Spoilers from the movie - Knives Out (2019). I want to investigate if the movie's plot operates correctly regarding the legal principle in question - Slayer Rule.

Millionaire Harlan Thornby bequeaths his entire estate to his nurse (but she doesn't know this). One night, she accidentally administers him a fatal dose of morphine. She looks for the antidote but cannot find it. Harlan Thornby would die in 10 minutes because there is no antidote. He sends her away and asks her to pretend everything is alright. And then slits his own throat with a knife and dies. His body is discovered next morning and the will is read.

Question: Was his throat-slitting necessary to protect the nurse from being disbarred from his inheritance? Does the throat slitting help or is she still disbarred?

  • Putting aside the legal issues, anyone give a lethal dose of morphine is going to be unconscious long before they can cut their own throat
    – Dale M
    Nov 25, 2019 at 4:49
  • @DaleM In the movie, it is established that he would have 10 minutes to live after the lethal dose. So they act in a matter of minutes. Nov 25, 2019 at 14:36
  • I’ve had morphine - you go off with the pixies is seconds.
    – Dale M
    Nov 25, 2019 at 19:06

2 Answers 2


Dying from one cause before another cause can take effect precludes the second cause from being the official cause of death, and therefore from the creation of liability for that second cause of death.

In the simplest case, such as this one, death by suicide precludes death by murder (with the exception of specific circumstances in some jurisdictions). If Thornby clearly and knowingly, without coercion, kills himself, there is no civil liability for wrongful death or criminal liability for homicide on the part of the nurse. The nurse is then not prevented from inheriting the wealth bequested to them - as would be likely if Thornby had died by the nurse's negligence.

  • Does it matter that he slit his throat BECAUSE he had been accidentally poisoned? There is causation here - isn't there. His suicide was predicated by the nurse's mistake. Does she escape all liability? Nov 25, 2019 at 3:57
  • If the poison caused a very painful death and he killed himself to avoid this, she would be liable (or say someone with a loaded gun is locked inside a burning house). In this case it seems the reason for killings himself is not the poison, but the intent that the nurse should inherit.
    – gnasher729
    Nov 25, 2019 at 8:49
  • @gnasher729 The body would be discovered only next morning. Would the autopsy be able to definitively establish whether the final cause of death was throat slitting or overdose since they happen literally minutes apart? Nov 25, 2019 at 14:35

It depends, mildly, on jurisdiction. In the US, there has been a political program of encoding common law principles into statutes. As an example, Arizona has a "slayer rule" statute, which states that

A person who feloniously and intentionally kills the decedent forfeits all benefits under this chapter with respect to the decedent's estate, including an intestate share, an elective share, an omitted spouse's or child's share, a homestead allowance, exempt property and a family allowance. If the decedent died intestate, the decedent's intestate estate passes as if the killer disclaimed that person's intestate share.

with numerous similar provisions. Moreover, the law holds that

"Felonious and intentional" means a conviction or a finding of guilty except insane for a homicide pursuant to section 13-1103, 13-1104 or 13-1105.

A possibly relevant question here is whether the nurse would be convictable under ARS §13-1103 (manslaughter), but this is only relevant in re-writing the movie. Arizona law requires an actual conviction, see Butwin v. Butwin et al.. Given that this is a hypothetical, we can then ask if a manslaughter conviction is legally possible. Conviction is possible for a person "Recklessly causing the death of another person". You should also note that the slayer rule does not include a conviction under ARS §13-1102, which is negligent homicide ("with criminal negligence the person causes the death of another person"). The circumstances described could sustain a negligent homicide conviction but not a regular manslaughter conviction.

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