According to the Crown Prosecution Service, "concealing an arrestable offence" is a criminal act - punishable by law.
"The offence of perverting the course of justice overlaps with a number of other statutory offences. Before preferring such a charge, consideration must be given to the possible alternatives referred to in this Charging Standard and, where appropriate, any of the following offences; Concealing an arrestable offence: s.5 Criminal Law Act 1967."
However, the UK Police take the view that no one is obliged to report a crime, (regardless of its seriousness)
"Whilst there is no legal requirement to report a crime, there is a moral duty on everyone of us to report to the police any crime or anything we suspect may be a crime." https://www.askthe.police.uk/content/Q514.htm
At the very least, these two statements prove that JW elders are im-moral when they choose not to involve the police in cases of alleged paedophilia.