This scares me, because I have plenty of old devices I no longer know the passwords for. I don't think I'm alone - plenty of people forget passwords they don't use in years.
If the police came and searched my house, they could probably find some ancient laptop or phone from a decade ago, demand I unlock it, and then put me in prison forever when I cannot do do so.
Also (this may be of limited consolation) the officer who compels you to disclose the key must have some idea of what data it is protecting in order to satisfy RIPA 2000 s 51(5)(a):
> The matters to be taken into account in considering whether the requirement [for proportionality] of subsection (4)(b) is satisfied in the case of any direction shall include... the extent and nature of any protected information, in addition to the protected information in respect of which the disclosure requirement is imposed, to which the key is also a key
Possibly could have gone differently if they had said they changed their 15 letter password every two weeks, but really?
If there's an excuse for something that is difficult to disprove because it's based on the word of the person it would undermine the justice system.
Imagine if ignorance of the law was an excuse.
CPS won’t (as a matter of policy, and also can’t afford to waste time and money) spend time trying to prosecute a forgotten password for old laptop, unless it’s connected to some other serious, evidenced, allegations.
(I was on a jury in just this situation. Reasonable doubt is a high bar and prosecutors know this).