Obligation to investigate 26. Under the obligation to respect and protect life the State should hold an independent investigation into a deprivation of life.227 This can be satisfied by an independent police investigation, but a national commission of inquiry has also been recommended.228 27. Such investigations must satisfy certain criteria: they must be carried out ‘promptly, thoroughly and effectively through independent and impartial bodies’.229 They must not be a mere formality.230 Other requirements are that:        The institution carrying out the investigation must comply with international human rights standards. The same will apply to military tribunals.231 The purpose of the investigation should be to determine the cause, time and manner of death and who was responsible.232 Individuals should be punished in a manner commensurate with the crimes they have committed.233 Those undertaking the investigation should have the necessary powers to access relevant documentation and information and to summon witnesses and other individuals.234 Those conducting the investigation and assisting it should be protected from reprisals.235 Relatives and legal representatives of the deceased should have access to any hearing, information and be also able to present information themselves. 236 A written report should be made available within a reasonable period of time237 and the results of any investigation must be made public, and include details of who undertook the investigation and how.238 227 McCann v UK, 27 September 1995. Jordan v UK, European Court, 4 May 2001. See e.g. Special Rapporteur on extrajudicial executions, A/HRC/8/3. 229 Human Rights Committee General Comment No.31, CCPR/C/21/Rev.1/Add/13 (2004), para 15. 230 Inter-American Court of Human Rights, Velásquez Rodríguez Case, Judgment of July 29, 1988, paragraph 177. 231 Report of the Special Rapporteur on extrajudicial, summary or arbitrary executions, E/CN.4/2006/53, 8 March 2006, para 37. 232 Principles on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, E.S.C. res. 1989/65, annex, 1989 U.N. ESCOR Supp. (No. 1) at 52, U.N. Doc. E/1989/89 (1989), Principle 9. 233 Report of the Special Rapporteur on extrajudicial, summary or arbitrary executions, E/CN.4/2006/53, 8 March 2006, para 39. 234 Principles on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, E.S.C. res. 1989/65, annex, 1989 U.N. ESCOR Supp. (No. 1) at 52, U.N. Doc. E/1989/89 (1989), Principle 10. 235 Principles on the Effective Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, E.S.C. res. 1989/65, annex, 1989 U.N. ESCOR Supp. (No. 1) at 52, U.N. Doc. E/1989/89 (1989), Principle 15. 236 Ibid, Principle 16. 237 Ibid, Principle 17. 238 E/CN.4/2005/7, paragraph 86. 228 56