Ransomware on an evidence computer could be hilarious... Even more so if it doesn't lock immediately but first waits to connect to a network and spread. Also because you don't want to be standing there when it happens (would get you arrested for a new crime on the spot).
You will need a very good lawyer to explain that you didn't hack them but they fucked up by trying to steal your data and "by accident" ran into a special file you had.
Then make sure you cannot legally be compelled to give them the decryption key. But I guess you should aways be able to "forget" the key, can't be forced to remember something.
That's assuming the individual is even aware that they're the attack vector. Apps can easily write a suitable file to their private storage that will deliver a payload.
And now I'm wondering - since the exploit only requires that the bad file be parsed, couldn't you put an appropriate exploit in place just by sending the file via email, sms, or airdrop? As long as it's someplace Cellbrite will see and process it, you're good.
You will need a very good lawyer to explain that you didn't hack them but they fucked up by trying to steal your data and "by accident" ran into a special file you had.
Then make sure you cannot legally be compelled to give them the decryption key. But I guess you should aways be able to "forget" the key, can't be forced to remember something.