Deterrence is aimed at dissuading the individual from re-offending (sometimes referred to as particular deterrence) as well as dissuading others from offending (general deterrence). Whilst there is widespread belief that deterrence (in either sense) works, there has been extensive debate about whether, in reality, it is effective. Considerable discussion about Deterrence may be read at "Deterrence - The Concept ..."
The evidence for the effectiveness of general deterrence was examined by a team from Cambridge University (at the request of the Home Office) and insufficent evidence was found that increases in the severity of sentences (as distinct from the risk of detection) had a significant effect on law-breaking - ( Von Hirsch, Bottoms et. al "Criminal Deterrence" 1999).
In English law, the purposes of sentencing (for adult offenders) are set out in the Criminal Justice Act 2003 s142. These are: (a) the punishment of offenders; (b) the reduction of crime (including its reduction by deterrence); (c) the reform and rehabilitation of offenders; (d) the protection of the public and (e) the making of reparation by offenders to persons affected by their offences. Item (b) is clearly based on the belief that deterrence will reduce crime.
The CJA 2003 does not guide the decision-maker (judge of magistrate) as to which purpose should prevail. This is left to the decision-maker's judgment taking into account all the relevant information about (a) the offence(s), (b) the offender(s) and perhaps the impact of the offence(s) on (c) the victim(s) and (d) the "community." (c) and (d) are controversial points in themselves but are not considered further here.
The various sentencing purposes can be in conflict. As Justice pointed out in 2003 - "... a rehabilitative sentence may not punish or deter; a sentence designed to deter others may inflict disproportionate punishment on this offender; a sentence aimed at punishment or deterrence may preclude the making of raparation; and so on...."
This lack of guidance is at variance with a Council of Europe recommendation made in 1992:
"Rationales for sentencing:
1. The legislator, or other competent authorities ....., should endeavour to declare the rationales for sentencing.
2. Where necessary, and in particular where different rationales may be in conflict, indications should be given of ways of establishing possible priorities in the application of such rationales for sentencing.
3. Wherever possible, and in particular for certain classes of offences or offenders, a primary rationale should be declared.
4. Whatever rationales for sentencing are declared, disproportionality between the seriousness of the offence and the sentence should be avoided."
The Halliday Report noted the Council of Europe's recommendations and proposed that neither deterrence nor incapacitation should be relied upon as a justification for sentencing - (see Report paras. 1.65 and 1.68).
Perhaps the key lies in proportionality. If this is applied to the case of a senior police officer for offences of perverting the course of justice then it is proportionality which will usually demand a stern sentence. This is justifiable by the details of the offence itself and the harm done to public confidence in the criminal justice system. Deterrence flows from such a sentence but is not the starting point for the sentencing process.
During 2009, the Court of Appeal handed down judgments relating to sentencing for burglary of occupied premises and gun crime. These point to a general raising of the tariff for such offences and this makes good sense since one would generally expect stern sentences for such harmful offences. However, it would appear that proportionality remains the key - proportionate to the harm the offence does to others.
The Sentencing Guidelines Council has published guidance about "Seriousness" and about sentencing for various types of offence.
Material from other countries:
New Zealand - Sensible Sentencing Trust
Judicial Commission of New South Wales