When the accused is charged with murder, the jury may return a verdict of manslaughter by suicide pact where they are satisfied that:
The prosecution has proven all of the elements of murder beyond reasonable doubt; and
The defence has proven, on the balance of probabilities, that the accused caused the death pursuant to a suicide pact (Crimes Act 1958 s6B(1)).
Unlike other forms of manslaughter, the maximum penalty for manslaughter by suicide pact is 10 years’ imprisonment (Crimes Act 1958 s6B(1A)).
There are three matters the defence must prove on the balance of probabilities to establish this partial defence:
There was an agreement between the accused and the deceased to seek the death of all parties to the agreement (a "suicide pact");
The accused’s acts that caused the death of the deceased were committed in pursuance of the suicide pact; and
At the time he or she caused the death, the accused had the settled intention of dying pursuant to the agreement (Crimes Act 1958 s6B(4)).
An agreement which has as its object the death of all of the parties to it will be a suicide pact, regardless of whether each party to the agreement is to take his or her own life (Crimes Act 1958 s6B(4)).
The accused must prove the existence of an actual suicide pact. It is not sufficient to prove that the accused held an honest and reasonable belief in the existence of a suicide pact (R v Iannazzone  1 VR 649).
Passively allowing another person to commit suicide or hasten his or her own death does not give rise to a suicide pact (H Ltd v J (2010) 107 SASR 352).
Onus of Proof
The accused bears the onus of establishing, on the balance of probabilities, that he or she killed the deceased pursuant to the suicide pact. If the accused fails to establish this matter, then the appropriate verdict will be guilty of murder (Crimes Act 1958 s6B(1). See also R v Sciretta  VR 139).
Liability of Third Parties
The existence of a suicide pact does not affect the criminal liability of a person who is a party to the homicide, but is not a party to the suicide pact (Crimes Act 1958 s6B(3)).
Suicide itself is no longer a crime (Crimes Act 1958 s6A).
Crimes Act 1958 s6B(2) creates three specialised suicide-related offences, which may be relevant where the accused’s actions did not directly cause the death of the deceased:
Inciting another person to commit suicide where the other person does so, or attempts to do so;
Aiding and abetting another person to commit suicide where the other person does so, or attempts to do so; and
Committing either of the above offences pursuant to a suicide pact (‘being a party to a suicide pact’).