26 TSALIKIDIS AND OTHERS v. GREECE JUDGMENT ECHR 2000-VII, and Mustafa Tunç and Fecire Tunç v. Turkey [GC], cited above, §§ 173-74). Moreover, there must be a sufficient element of public scrutiny of the investigation or its results to secure accountability in practice. In all cases, the victim’s next of kin must be involved in the procedure to the extent necessary to safeguard his or her legitimate interests (see Aliyeva and Aliyev v. Azerbaijan, no. 35587/08, § 70, 31 July 2014). 88. In particular, the investigation’s conclusions must be based on thorough, objective and impartial analysis of all relevant elements. Failing to follow an obvious line of inquiry undermines to a decisive extent the investigation’s ability to establish the circumstances of the case and the identity of those responsible. Nevertheless, the nature and degree of scrutiny which satisfy the minimum threshold of the investigation’s effectiveness depend on the circumstances of the particular case. The nature and degree of scrutiny must be assessed on the basis of all relevant facts and with regard to the practical realities of investigation work. (see Armani Da Silva v. the United Kingdom [GC], cited above, § 234). 89. The Court has held that in some cases information purportedly casting new light on the circumstances of a killing may come into the public domain at a later stage. The issue then arises as to whether, and in what form, the procedural obligation to investigate is revived. To that end, the Court considered in its judgment in the case of Brecknell v. the United Kingdom (no. 32457/04, § 71, 27 November 2007) that, where there is a plausible or credible allegation, the discovery of any new piece of evidence or item of information relevant to the identification and eventual prosecution or punishment of the perpetrator of an unlawful killing would require the authorities to take further investigative measures. The steps which would be reasonable to take will vary considerably according to the facts of the situation. The lapse of time will, inevitably, be an obstacle as regards, for example, the location of witnesses and the ability of witnesses to recall events reliably. Such an investigation may in some cases, reasonably, be restricted to verifying the credibility of the source or of the purported new evidence (see Gasyak and Others v. Turkey, no. 27872/03, § 60, 13 October 2009). 90. The extent to which the requirements of effectiveness, independence, promptness and expedition, accessibility to the family and sufficient public scrutiny apply will again depend on the particular circumstances of the case, and may well be influenced by the passage of time as stated above. Where an allegation or new evidence tends to indicate police or security force collusion in an unlawful death, the criterion of independence will, generally, remain unchanged (see, for the importance of this criterion from the very earliest stage of the procedure, Ramsahai and Others v. the Netherlands [GC], no. 52391/99, §§. 325, 333-341, ECHR 2007-II). Promptness will be unlikely to come into play in the same way, since, for example, there may be no urgency as regards the securing of a crime scene from contamination