The military conflict in Afghanistan has, once again, brought to the attention of politicians, the public and the press, the dangers of serving in the armed forces and the difficulties the personnel experience once they have finished active service. There is concern that a proportion of armed forces personnel experience problems when leaving military service and returning to civilian status
. While the majority of armed forces personnel manage this transition
, some experience a range of difficulties. These include mistrust
, particularly for those over 25 years of age
[5, 6], boredom, a lack of money
[8, 9], on-going poor mental health
[2, 6, 10, 11], and suicidality
[12–14]. While the definition of ‘military veteran’ differs between countries (see Dandeker et al. for an overview of definitions
), concern has also been voiced that the complex needs of recently deployed military veterans in both the United States (US)
 and the United Kingdom (UK)
 could increase their future contact with criminal justice services.
Since the mid-1980s, when the number of veteran prisoners peaked at 21% of all US prisoners, there has been a slow decline in the number of incarcerated military veterans
. The last available figures report that 10% of US Federal and State prisoners are veterans
, however this relates to data gathered in 2004. Within the UK, and while the exact number of veterans is probably unknown
, the Home Office suggested that at the beginning of the last decade around 3% of prisoners were military veterans
. More recent figures for the number of veterans in prison range from 3.5%
 to 8.5%
. Figures proposed for the number of people supervised by UK probation services who have veteran status also differ ranging from 3.4%
 to 6%
. Such disparity indicates a degree of uncertainty over the actual number of veterans in UK prisons.
Although societal challenges, such as soldiers returning from war, and different periods in time may influence the risk of veteran imprisonment
, debates on whether military service causes future offending have been longstanding. For example, accounts of such arguments are evident after the Second World War
. However, more recently, Bouffard
 found no relationship between military service and subsequent criminal or violent behavior, finding instead that military service reduced future criminality. Conversely, Galiani and colleagues
 found that conscripted military service is positively related to future criminal behavior and conviction. These contrary views may be attributable to the ‘type’ of person engaged in military service and not the service per se. Personal characteristics and the ‘quality’ of the individual, such as educational attainment, anti-social traits or mental health problems
, may have stronger influences on the likelihood of future offending and incarceration than the engagement of military service
Military veterans experiencing mental health difficulties, particularly post-traumatic stress disorder (PTSD) and combat related stress, is not a new phenomenon
[31, 32]; however, veterans with mental health difficulties can find themselves imprisoned
. Black and colleagues
 found that incarcerated veterans had a higher frequency of psychiatric illness than non-imprisoned veterans. They also found that veteran incarceration was associated with high healthcare utilization and contact with mental health professionals.
Military veterans with PTSD
[33–35] or combat experience
 may find themselves incarcerated, yet the associations between PTSD or combat exposure and imprisonment are not without ambiguity
[30, 33, 36]. Despite the uncertainty of a direct relationship with imprisonment, combat exposure has been strongly associated with aggressive tendencies
, drug use
, alcohol consumption
, and engaging in risk taking behaviors
. Further, while veterans with PTSD may find themselves imprisoned, the prevalence of PTSD in military personnel and veterans shows variability across countries
. For UK veterans PTSD is less common than depression
, and both depression and alcohol abuse appear more problematic
Alcohol use is part of the social fabric of some armed forces and alcohol problems within the military are not a new phenomenon. Wagley
 comments with concern on the number of military offenders with alcohol problems requiring offender rehabilitation post World War II. More than half a century later excessive alcohol use by military personnel is still evident. Excessive use of alcohol has been found to be more common in UK military personnel than the UK general population
, with alcohol misuse the most common mental health problem found in new military veterans
. Alcohol and other drugs may be used to gain relief from, and cope with, the psychological consequences of combat exposure
[3, 34]. For example, a relationship exists between excessive alcohol use and combat exposure
[38, 44, 45]. Alcohol misuse in veterans can also contribute to imprisonment
While alcohol misuse is common across veteran age groups, some younger veterans are also using drugs
. Substance use was evident among military personnel during the Vietnam War
 and, while the majority stopped such use following discharge
, small numbers continued
[33, 49]. It is recognized that substance use can contribute to the incarceration of veterans
[17, 18, 46, 50]. For example, incarcerated Vietnam veterans were more likely to have substance use problems than their non-convicted counterparts
, use which might not be attributable to their military service. Veterans who continued opiate use after returning from Vietnam (and after ending their military career) tended to, among other factors, have pre-enlistment substance use and engagement in deviant activities
In summary, despite current concerns, veteran contact with criminal justice systems is not a new phenomenon and a number of contributory factors have been reported. Previous research, as discussed above, has identified veteran poor mental health, alcohol and substance use, and the consequences of exposure to combat as having an impact on veterans returning to a civilian life. These may also contribute to their contact with criminal justice systems. However, there is no consensus on this and other reasons have been suggested. This review looks to resolve this by identifying whether the above are contributory factors to military veterans having contact with criminal justice systems and whether such factors provide an additional risk to said contact when compared with mentally healthy military veterans.
Aims and objectives
The primary objectives of the review are to:
Synthesize the evidence on the amount and type of contact with criminal justice systems for those military veterans with mental health problems, including substance use compared to those veterans who do not have such problems.
Synthesize the evidence on the views and experiences of military veterans with mental health and/or substance misuse problems on their experiences regarding contact with criminal justice services and what they perceived contributed to, or influenced, their contact with said services.
Use the synthesis of the qualitative studies to illuminate and explain the results from the quantitative synthesis.
In addition to the above, and with specific reference to military veterans with mental health problems, the review will also seek to address the following supplementary questions:
are there differences in types of criminal justice contact or military experience and;
are there international and temporal differences in veteran contact with criminal justice services, and if so how do these contact types differ.
If studies are available international comparisons will focus on the US, UK, Australia, New Zealand, Canada and European Union Countries. Comparison of temporal differences will focus on the immediate years after key conflict periods, namely World War 2, Korean War, Vietnam War, Falklands Conflict, 1st Gulf War, 2nd Gulf War and the Afghanistan conflict.