The police investigating the crime called her a witness, legal adviser to lawyer is a ridiculous unbelievable leap from me, fantastically sorry about that........
As for mother informing the child, the last line is ambiguous at best, in 99.9999% of cases it would be read as the child informing the mother about it, not the other way around. its a little ambiguous as the "child" is both now 30 and has downs syndrome.
So the choices here are, the mother knew about it at the time, the child forgot and the mother randomly chose 14 years later to tell everyone including her daughter about it, which unfortunately in this world is possible, woman looking for damages and a payout. The other choice is the "kid" said nothing at the time and years later told her mother, this would be the far more likely reading of it in 99% of cases.
Again, it has NOTHING to do with what the op is talking about. It's not the same situation and again the "legal adviser" was NOT arrested for making false claims, or misleading the mother, or knowingly helping someone who was lying, he was arrested for (seemingly) attempting to disturb the peace. You can't read between the lines, there is next to no information both about the case, nor about the reason for the arrest(as he was supposedly on his way to a what sounds like a protest).
The story is about the legal adviser more than the case, and the OP is essentially wondering what to do to help his friend, these are ENTIRELY unrelated.
Doing nothing because someone else in another case MIGHT not be telling the truth, is ridiculous.