If he's an accomplice, them charge him with that, and turn it into a classical prisoner's dilemma. Don't just make up bullshit charges, that's abuse of the justice system.
In this case the person did a little more than Jaywalking so they're on the hook for more. It's also possible to have information on a criminal act or conspiracy without being an accomplice.
I appreciate the extremely... principled morality of some here, but the law isn't an ethical framework, it's a practical one informed by ethical principles. It's also not a computer program, people are involved who make decisions based on a number of factors ranging from professional and selfless, to careerist and selfish. That's life.
A really easy way to avoid all of this is to stay out of the system, it's not as though he's in for stealing a loaf of bread to feed his starving child.