Serial rapists are far more common than previously thought, analysis of 5,000 rape kits dating back more than 20 years has revealed.

Scientists in Ohio, United States, announced their findings after testing the backlog of rape kits, which were used between 1993 and 2010.

Analysis of the kits – used to collect evidence from the victims of sexual attacks - has given the researchers greater insight into the behaviour of sexual predators.

More than 250 people have already been convicted of sexual offences as a result of the tests and investigators expect the prosecutions to continue.

The Cuyahoga County Sexual Assault Kit Task Force – a multidisciplinary body dedicated to following up sexual assault cases stemming from the untested kits – worked with the Begun Centre for Violence Prevention Research and Education at Case Western Reserve University, who study violence and its prevention, to gain an insight into patterns revealed by the kits.

Starting in 2014, the task force say the discovery that serial rapists are much more common than previous studies have suggested could change the way sexual assaults are investigated.

Of 243 sexual assaults studied, 51 per cent were tied to serial offenders, who tended to have more extensive and violent criminal histories than one-off sexual offenders.

“Our findings suggest it is very likely that a sexual offender has either previously sexually assaulted or will offend again in the future,” said Rachel Lovell, senior research associate at the Begun Centre.

“Investigating each sexual assault as possibly perpetrated by a serial offender has the potential to reduce the number of sexual assaults if investigations focus more on the offender than on single incidents.”

Countries where sexual violence has become a way of life Show all 19 1 /19 Countries where sexual violence has become a way of life Countries where sexual violence has become a way of life Afghanistan Recommendation: I urge the Government of Afghanistan to adopt legislative reforms to ensure that sexual violence offences are not conflated with adultery or “morality crimes” and to establish infrastructure for the delivery of protection, health and le gal services to survivors. I call on the Ministry of the Interior to accelerate efforts to integrate women into the Afghan National Police, thereby enhancing its outreach and its capacity to address sexual and gender-based violence Countries where sexual violence has become a way of life Central African Republic Recommendation: I urge the authorities of the Central African Republic to ensure that efforts to restore security and the rule of law take into account the prevention of sexual violence and that monitoring of the ceasefire and peace agreement explicitly reflects this consideration, in line with the joint communiqué of the Government and the United Nations on the prevention of and response to conflict-related sexual violence signed in December 2012. I further encourage the authorities to make the rapid response unit to combat sexual violence operational and to establish a special criminal court Countries where sexual violence has become a way of life Colombia Recommendation: I commend the Government of Colombia for the progress made to date and its collaboration with the United Nations, including through the visit of my Special Representative on Sexual Violence in Conflict in March 2015. I encourage the authorities to implement Law 1719 and continue to prosecute cases of sexual violence committed during the conflict to ensure that survivors receive justice and receive reparations. Conflict-related sexual violence should continue to be addressed in the Havana peace talks, as well as in the resulting accords and transitional justice mechanisms. Particular attention should be paid to groups that face additional barriers to justice such as ethnic minorities, women in rural areas, children, lesbian, gay, bisexual, transgender and intersex individuals and women abused within the ranks of armed groups. I encourage the Government to scale up its protection measures and share its good practices with other conflict-affected countries Countries where sexual violence has become a way of life Congo Recommendation: I urge the Government of the Democratic Republic of the Congo to ensure full implementation of the armed forces action plan against sexual violence, to systematically bring perpetrators to justice and to deliver reparations to victims, including payment of outstanding compensation awards. I call on donors and the United Nations system to support the Government in its efforts and to pay increased attention to neglected areas, including unregulated mining regions Countries where sexual violence has become a way of life Iraq Recommendation: I commend the Government of Iraq for its national action plan for the implementation of Security Council resolution 1325 (2000) and urge its swift implementation, including by training its security forces to ensur e respect for women’s rights. Programmes to support the social reintegration of women and girls released from captivity by ISIL are urgently needed, as is community-based medical and psychological care. The capacity of the United Nations system should be enhanced through the deployment of Women’s Protection Advisers or equivalent specialists Countries where sexual violence has become a way of life Libya Recommendation: I urge the national authorities in Libya to implement Decree No. 119 and Resolution 904 of 2014 to ensure redress for all victims, including those affected by the current conflict, through the establishment of multisectoral services and the adoption of legislation to categorically prohibit sexual violence Countries where sexual violence has become a way of life Mali Recommendation: I urge the Government of Mali, with support from United Nations Action against Sexual Violence in Conflict, to develop a comprehensive national strategy to combat sexual and gender-based violence and to ensure the safety of humanitarian workers so that services can reach remote areas. I further call on all parties to ensure that conflict-related sexual violence is addressed in the inter-Malian dialogue and that perpetrators of sexual violence do not benefit from amnesty or early release Countries where sexual violence has become a way of life Myanmar Recommendation: I urge the Government of Myanmar to continue with its reform agenda and, in the process, take practical and timely actions to protect and support survivors of conflict-related sexual violence and to ensure that security personnel accused of such crimes are prosecuted. Sexual violence should be an element in all ceasefire and peace negotiations, excluded from the scope of amnesty provisions and addressed in transitional justice processes. It is critical that women be able to participate consistently in and influence these processes Countries where sexual violence has become a way of life Somalia Recommendation: I reiterate my call to the Federal Government of Somalia to implement the commitments made under the joint communiqué of 7 May 2013 and its national action plan to combat sexual violence in conflict, including specific plans for the army and the police. I encourage the adoption of a sexual offences bill as a matter of priority Countries where sexual violence has become a way of life South Sudan Recommendation: I urge the parties to the conflict in South Sudan to adopt action plans to implement the commitments made under their respective communiqués. I call upon the Government of South Sudan to address the negative impact of customary law on women’s rights and to reflect international human rights standards in national law. I also encourage the African Union to make public and act upon the report of its Commission of Inquiry on South Sudan Countries where sexual violence has become a way of life Sudan (Darfur) Recommendation: I call upon the Government of the Sudan to grant the United Nations and its humanitarian partners unfettered access for monitoring and the provision of assistance to people in need in Darfur. Given that there has been grave concern over sexual violence in Darfur for more than a decade, I encourage the Government to engage with my Special Representative on Sexual Violence in Conflict to develop a framework of cooperation to address the issue comprehensively Countries where sexual violence has become a way of life Syria Recommendation: I acknowledge the Government’s invitation to my Special Representative to visit the Syrian Arab Republic and call upon the authorities, in the context of such a visit, to agree on specific measures to prevent sexual violence, including by members of the security forces. I condemn the use of sexual violence by ISIL and all other parties listed in the annex to the present report and call on them to cease such violations immediately and allow unfettered access for the delivery of humanitarian assistance Countries where sexual violence has become a way of life Yemen Recommendation: I urge the authorities in Yemen to undertake legislative reform as a basis for addressing impunity for sexual violence, ensuring the provision of services for survivors and aligning the minimum legal age of marriage with international standards. I further call on the authorities to engage with local community and faithbased leaders to address sexual and gender-based violence and discriminatory social norms Countries where sexual violence has become a way of life Bosnia and Herzegovina Recommendation: I urge the relevant authorities in Bosnia and Herzegovina to harmonize legislation and policies so that the rights of survivors of conflict-related sexual violence to reparations are consistently recognized and to allocate a specific budget for this purpose. I further call upon the authorities to protect and support survivors participating in judicial proceedings through, inter alia, referrals to free legal aid, psychosocial and health services, as well as economic empowerment programmes Countries where sexual violence has become a way of life Ivory Coast Recommendation: I urge the Government of Côte d’Ivoire to ensure the effective implementation of its national strategy to combat gender-based violence and the action plan for FRCI, and call on the international community to support these efforts. It is critical to accelerate disarmament, demobilization and reintegration and strengthen law enforcement to ensure that ex-combatants who have been reintegrated into the transport sector do not pose a risk to women and girls who are reliant on those services. The Government and the international community must provide monitoring and awareness-raising to mitigate the possibility of a recurrence of sexual violence in the context of the presidential elections to be held in October 2015 Countries where sexual violence has become a way of life Liberia Recommendation: I call on the Government of Liberia to continue its critical efforts to combat sexual and gender-based violence including through the United Nations-Government of Liberia Joint Programme, and in the context of recovery from the Ebola virus epidemic Countries where sexual violence has become a way of life Nepal Recommendation: I encourage the Government to ensure that survivors of conflict-related sexual violence are recognized under the law as “conflict victims”, which will enable them to access services, judicial remedies and reparations. I further call on all parties involved in the transitional justice process to ensure that the rights and needs o f survivors of sexual violence are addressed in institutional reforms and that these crimes are excluded from amnesties and statutes of limitations Countries where sexual violence has become a way of life Sri Lanka Recommendation: I call upon the newly elected Government of Sri Lanka to investigate allegations of sexual violence, including against national armed and security forces, and to provide multisectoral services for survivors, including reparations and economic empowerment programmes for women at risk, including war widows and female heads of household Countries where sexual violence has become a way of life Nigeria Recommendation: I encourage the Government to implement its national action plan on the implementation of Security Council resolution 1325 (2000) to ensure that women’s protection concerns are mainstreamed throughout its security operations. I also call upon the authorities to guarantee security in and around internally displaced persons camps and to extend medical and psychosocial services to high-risk areas

The researchers also found many rapists have long criminal histories, often beginning before their first documented sexual assault and continuing after it. Seventy-four per cent of serial rapists were found to have been arrested before the sexual attack and 95 per cent had been arrested afterwards.

In contrast, for one-off rapists, the figures were 51 per cent and 78 per cent respectively.

The different types of offenders were also found to behave differently during the course of their crimes, the researchers said.

Sexual assaults committed by serial offenders more frequently involved kidnapping victims and threatening them, the researchers found. Serial offenders were also less likely to be known to their victim.

But sexual assaults committed by serial offenders less frequently involved restraining victims and injuring them in order to complete the attack. However, one-off offenders were more likely to punch, slap, hold down or restrain a victim.

One-off offenders were more likely to attack in their own house or the house of the victim. However, 58 per cent of serial offenders committed all of their crimes in the same type of setting, such as a vehicle.