The courts have developed a number of specific principles concerning the factors a court should take into account when sentencing for conspiracy offences.
The High Court (Gummow, Hayne, Crennan, Kiefel and Bell JJ in a joint judgment, Heydon J agreeing) explained the nature of the crime of conspiracy and what must be proved in The Queen v LK (2010) 241 CLR 177 at :
the prosecution must establish that the accused entered into an agreement with one or more other persons and that he or she and at least one other party to the agreement intended that the offence particularised as the object of the conspiracy be committed pursuant to the agreement. Proof of the commission of an overt act by a party to the agreement conditions guilt and is placed on the prosecution to the criminal standard.
The Crown does not have to prove a causal nexus between the conspiracy and its object. The focus of the conspiracy is what the conspirators intended to bring about, not whether the object was achieved: Dickson v R  NSWCCA 105 at –.
Conspiracy is a continuous crime, extending over the period of agreement until the police intervene or the objective of the agreement is achieved: R v Masters (1992) 26 NSWLR 450 at 458.
For State offences the common law offence of conspiracy applies unless a statute provides otherwise: see NSW statutory conspiracy offences at [65-400]. The penalty for common law conspiracy is at large. Section 11.5 Criminal Code (Cth) applies in the case of offences against the Commonwealth subject to any specific offence provisions. The words “conspires” and “conspiracy” in s 11.5(1) are to be understood as fixed by the common law subject to express statutory modification: The Queen v LK at .
[65-320] Overt acts in furtherance of the conspiracy
The degree to which a sentencing judge can make findings of fact about, and take into account, evidence concerning acts undertaken in furtherance of a conspiracy will often be in issue. The court is not confined to consideration of the agreement itself: Savvas v The Queen (1995) 183 CLR 1 at 8. The general principle is that where a court is sentencing for the crime of conspiracy, it may take into account the overt acts of the conspiracy insofar as they bear upon the “content and duration and reality of the conspiracy” and indicate the true nature of and degree of criminality involved in the conspiracy: R v Savvas (No 2) (1991) 58 A Crim R 174 at 178; Savvas v The Queen (1995) 183 CLR 1 at 11, 13, 17; Truong v The Queen (2004) 223 CLR 122 at ; Ansari v R (2007) 70 NSWLR 89 at .
The court may refer to what was actually done in the transaction of the conspiracy and may take into account the fact that the object of the conspiracy was implemented: Savvas v The Queen at 7-8; R v DW (2012) 221 A Crim R 63. The conspiracy does not end with the making of the agreement it continues as long as there are two or more parties to it intending to carry it out: DPP v Doot (1973) AC 807 at 823 quoted with approval in Savvas v The Queen at 8. In Savvas v The Queen, the High Court held that notwithstanding the offences charged were conspiracies, the sentencing judge was entitled to take into account that the heroin was in fact imported and distributed pursuant to the conspiracy, and that the appellant was involved in those events: Savvas v The Queen at 7, 9. To do so did not contravene the principle in The Queen v De Simoni (1981) 147 CLR 383. The sentencing judge was not confined to sentencing the appellant on the narrow basis of what he actually physically did. However, the High Court noted at 8:
The line is sometimes a fine one to walk but it has to be walked if a conspiracy charge is brought and the accused is convicted.
In Truong v The Queen (2004) 223 CLR 122, the High Court applied Savvas v The Queen at :
Savvas is authority for the proposition that, if [Truong] had been tried for, and convicted of, conspiracy rather than the substantive offences, the kidnapping and the killing would have been matters for the sentencing judge to take into account, being aspects of “the degree of criminality involved in the appellant's participation in the conspiracy”.
In many cases the overt acts in furtherance of the conspiracy constitute a substantial part of the evidence from which the existence of the agreement in question is to be inferred: R v Savvas (No 2) (1991) 58 A Crim R 174 at 176.
However, where a court imposing a penalty for conspiracy, takes into account the overt acts of the conspiracy, it would be wrong to impose a further penalty with respect to those acts. Prosecutions for conspiracy and for a substantive offence ought not result in a duplication of penalty: The Queen v Hoar (1981) 148 CLR 32 at 38.
The fact that an attempt is foiled does not lessen the seriousness of what was intended to be achieved by the conspiracy. For example, in Thangavelautham v R  NSWCCA 141, a conspiracy to defraud case, the court held that in circumstances where the object of the conspiracy was to obtain the details of a significant number of individuals’ credit card information, it was not required that the applicant be sentenced by reference to a single offence under s 192E Crimes Act 1900: Thangavelautham v R at .
[65-340] Yardstick principle — maximum penalty for substantive offence
Where the conspiracy relates to a specific statutory offence, the maximum penalty for the substantive offence should be used as a yardstick during the sentencing process: The Queen v Hoar (1981) 148 CLR 32 at 39; Vella v R  NSWCCA 148 at . The penalty for the conspiracy should generally not exceed that provided for the substantive offence: The Queen v Hoar at 40; Verrier v DPP (1967) 2 AC 195. However, in exceptional cases, the element of concert may justify a more severe penalty for the conspiracy than for the substantive offence: The Queen v Hoar at 38; Thangavelautham v R  NSWCCA 141 at . Further, where the conspiracy is to commit a number of offences, then the court should have regard to the maximum penalty that can be imposed with respect to each of those offences: The Queen v Hoar at 40.
The NSW Court of Criminal Appeal affirmed the “yardstick” principle described in The Queen v Hoar in Bell v R  NSWCCA 206 at  and Pettersen v R  NSWCCA 20. In Pettersen v R at , a conspiracy to break, enter and steal, the court held that the penalty for a common law conspiracy is at large subject only to a requirement that the sentence imposed not be excessive.
In some cases, the result of an instinctive synthesis of all the relevant factors may result in a sentence at or close to the maximum penalty for the substantive offence: Dickson v R  NSWCCA 105 at –. In Dickson v R, the sophistication, planning and complexity of a conspiracy to defraud the Commonwealth under s 135.4 Criminal Code (Cth) justified the finding that the offence was in the “worst category of cases”: Dickson v R at .
[65-360] Role of the offender
A relevant consideration in sentencing for conspiracy, particularly where the conspiracy relates to a drug offence, is the role played by the offender: Tyler v R (2007) 173 A Crim R 458 at ; The Queen v Olbrich (1999) 199 CLR 270 at ; an assessment of culpability of each offender requires precise identification of his or her criminal conduct constituting the offence: R v Shore (1992) 66 A Crim R 37. However, when identifying the role of a participant in a conspiracy by reference to their position in the organisational hierarchy, the precise physical acts of the participant are relevant only as one part of a complex tapestry. To isolate the physical acts of the conspirator and sentence them for those acts alone would be artificial and ignore the complex interconnection between participants and the organisational nature of a conspiracy. Further, it ignores the essential feature of the offence of conspiracy – the agreement to participate in an organised criminal activity: Alpha v R  NSWCCA 292 at .
In Diesing v R  NSWCCA 326, the court referred to Tyler v R and stated at  that their findings:
… do not seek to punish the applicant for offences with which he was not charged … They reflect upon the degree of the criminality involved in the applicant’s participation as a principle in a conspiracy, extending over five months and constituting a large-scale commercial operation spanning two states.
Those who play an authoritative or managerial role in a conspiracy to import prohibited drugs will usually receive a greater sentence than those whose role is less: Alpha v R at ; Tyler v R at –. Conversely, couriers will usually be sentenced less harshly than those who occupy more senior positions: Tyler v R at –. To treat an offender as more culpable because of his or her close physical connection to the drugs would invert the conventional approach to blameworthiness in drug conspiracies: Tyler v R at .
However, there is a danger in describing the offender’s role in terms of “further offences committed by the prisoner” as this has the potential to give rise to a belief that the prisoner is being dealt with for something which has not been the subject of a charge: Savvas v The Queen at 7. When sentencing for conspiracy cases care must be taken not to breach the principle in The Queen v De Simoni (1981) 147 CLR 383 by punishing an offender for an offence for which he or she has not been convicted.
If an offender enters into an agreement but chooses to abandon any participation in the substantive offence, that fact can be taken into account as a matter in mitigation: Savvas v The Queen (1995) 183 CLR 1 at 7; and see M Wasik, “Abandoning criminal intent” (1980) Crim LR 785 referred to in R v Wright (unrep, 8/7/97, NSWCCA). The fact that the conduct contemplated is impossible has also been taken into account in mitigation: R v El Azzi (2001) 125 A Crim R 113 at .
[65-380] Standard non-parole period provisions
The standard non-parole period provisions do not apply to offenders charged with common law conspiracy: Diesing v R  NSWCCA 326 at ; Greenaway v R  NSWCCA 270 at ; SAT v R  NSWCCA 172 at . There is a 10-year standard non-parole period for the offence of conspiracy to murder under s 26 Crimes Act 1900: see “Conspiracy to murder” in NSW statutory conspiracy offences at [65-400].
[65-400] NSW statutory conspiracy offences
Drug conspiracy offences
Section 26 Drug Misuse and Trafficking Act 1985 provides that a person who conspires with another person or other persons to commit an offence under Division 2 of Part 2 is guilty of an offence and liable to the same punishment, pecuniary penalties and forfeiture as the person would be if the person had committed the first-mentioned offence.
For drug conspiracy offences reference should be made to the relevant offence provision and Section 26 — Conspiracy offence at [19-855].
Conspiracy to murder
As to conspiracy to murder see Conspiracy/solicit to murder: s 26, Crimes Act 1900 at [30-090].
See MP v R  NSWCCA 226 and s 51C Firearms Act 1996: conspiring to commit offence outside NSW.
[65-420] Commonwealth conspiracy offences
Commonwealth conspiracy offences are addressed by statute. Section 11.5 Criminal Code (Cth) (Conspiracy) sets out the statutory requirements governing conspiracy in respect of Commonwealth offences. For example, s 11.5(1) provides that a person who conspires with another person to commit an offence punishable by imprisonment for more than 12 months, or by a fine of 200 penalty units or more, is guilty of the offence of conspiracy to commit that offence and is punishable as if the offence to which the conspiracy relates had been committed.
Commonwealth legislation also provides a number of specific conspiracy offences including conspiracy to defraud the Commonwealth under s 135.4 Criminal Code (Cth) (previously ss 29D and 86 Crimes Act 1914 (Cth)). In sentencing for this offence, the court can have regard to the diminution of the maximum penalty from 20 years under the old statutory regime (s 86) to 10 years under the new regime (s 135.4(3) Criminal Code (Cth)) as reflecting a change in attitude towards fraud on the part of the legislature: R v Ronen (2006) 161 A Crim R 300 per Spigelman CJ at  and R v Boughen (2012) 215 A Crim R 476. See also Agius v The Queen (2013) 248 CLR 601; Vella v R  NSWCCA 148; Liles v R (Cth)  NSWCCA 289; R v Mereb  NSWCCA 149; Sakovits v R  NSWCCA 109; Elomar v R  NSWCCA 303.
For a “worst category” case of conspiracy to defraud the Commonwealth under s 135.4 Criminal Code (Cth), see Dickson v R  NSWCCA 105.
Sections 41 and 42 Crimes Act 1914 (Cth) provide for the offence of conspiracy to pervert the course of justice.