A/HRC/14/24 should undertake periodic reviews to determine whether international standards have been complied with, and report to the Council on their findings (E/CN.4/2005/7, paras. 60-62, 88); (c) International law prohibits the application of the death penalty to juveniles;18 (d) International law prohibits the mandatory imposition of the death penalty;19 (e) International law only permits the death penalty for “the most serious crimes”. The scope and implications of this important phrase have been explored in detail;20 (f) A person sentenced to death has the right to seek pardon or commutation of the sentence (A/HRC/8/3, paras. 59-67). 52. In the death penalty context it has also been necessary to address the relationship between international legal obligations and sharia law or Islamic criminal law as applied in some countries. Specifically, reports have discussed stoning, the illegality of the death penalty for homosexuality or adultery, and the challenges of diyah (compensation in lieu of criminal punishment).21 G. Impunity: investigation, prosecution and conviction 53. Impunity is often a central cause of continued killings. In many of the countries visited, impunity is maintained through problems at every level of the criminal justice system. Thus, police may be unwilling or unable to carry out an independent investigation of the killing. The State may lack forensic capacity to conduct investigations. Crimes scenes may not be secured. The police may fail to refer cases to the prosecution service. Prosecutors may be corrupt or poorly trained. Witnesses may justifiably be unwilling to testify because of inadequate witness protection programmes. Judges’ dockets may be so overcrowded that cases are delayed for years, or judges may also take bribes to delay cases or absolve perpetrators. If perpetrators are convicted, prison systems may be insecure or susceptible to corruption, resulting in prisoners escaping or bribing their way out of detention. 54. In response to these challenges, specific studies have addressed: (a) The need for external oversight of the police, including a study of the various forms of oversight, and the applicable law and principles (A/HR/14/24/Add.8); (b) The obstacles to effective national commissions of inquiry, and the requirements for the creation and implementation of effective commissions;22 (c) Best practices in witness protections programmes (A/63/313); (d) How States can make their military justice systems compatible with human rights standards (A/63/313). 18 19 20 21 22 A/HRC/11/2, paras. 29-42 and A/HRC/4/20, paras. 16-17 and 63. E/CN.4/2005/7, paras. 63-64 and 80; A/HRC/4/20, paras. 54-62 and 66; and A/HRC/11/2/Add.6, paras. 83-84 and 115. A/HRC/4/20, paras. 39-53 and 65; A/HRC/11/2/Add.6, para. 84; and A/HRC/11/2/Add.5, para. 23. A/HRC/8/3/Add.3, paras. 76-78; E/CN.4/2006/53/Add.4, paras. 21-24 and 32-38; and A/61/311, paras. 55-64. A/CN.4/2006/53 and A/HRC/8/3. 13