Four years ago my then partner's son stole and pawned my jewellery. I reported it to the police but my ex put pressure on me not to press charges. I have a handwritten confession from his son and evidence from the pawnbrokers. Can I still press charges? His son is still thieving and I think he needs to be taught a lesson.

No, it's too late. I'm also sure the Police aren't happy if you filed charges and then recanted.

Move on.

I really can't say it's too late, because I really don't know the laws concerning this. If I were you, I would contact a lawyer where you live, and find out. It probably wouldn't cost you anything to have an initial conference, and be sure to ask the lawyer what the charge would be, just to talk about it first. Good luck.
PS; Your handwritten note from the accused might go a long way in this for you.
I am 71 yrs old, and have seen some really unusual results from courts about thefts.

Why is this a matter for a Lawyer? It's a criminal case, not a civil case. OP doesn't need an Attorney. She filed charges once. She then withdrew her complaint or dropped the charges or whatever else happened. The Police Department should not be used as a threat or to teach people lessons.

This happened 4 years ago when OP was dating the father. Now the relationship is over and she wants to press charges - again. It's going to look like what it very well could be - "gotcha."

Anyway, how do you see an Attorney assisting her?

I see a lawyer telling her whether it's practical to pursue this further in court, trying to get her money back. He stole from her! I would certainly try to get it back, even though I changed my mind a few years earlier. That's what I would do. If she does nothing, she has NO chance of getting any money back.

Fred, she doesn't want her money back. She wants to teach him a lesson.

She wants to PRESS CHARGES, not sue him civilly.

If you want to go off in another direction, we can do that. In the meantime I answered what she asked.

And "his" defense - I stole, I admitted it, she had me arrested/tried to have me arrested, she dropped the charges. She forgave the "debt."

To update my situation regarding previous answers. I wanted to press charges at the time but was pressured not to by my abusive former partner. I'm not being vindictive regarding his son due to the breakup of the relationship (this happened two years ago when I finally managed to get free). The boy, who's now 20, has continued to steal from various family members as well as from strangers on the street. I feel he needs to pay for his actions. So far his father has protected him by paying people off/threatening them, so no further action is taken. The lad is out of control, he has no remorse for his actions. The confession I had from him wasn't an apology and I certainly never forgave him. He admitted taking my jewellery 'to get it polished'. It had been pawned (even though he was only 17 at the time). The pawn shop identified him. He had brought in items not just stolen from me, but from strangers off the street whom he had mugged. He is a one-man crime wave. He has physically attacked not just myself, but many others (with knives and bricks). He deserves to be punished and I finally have the strength to see it through. But is there a limit until how long after a crime has been committed to press charges? Would a court understand that I was placed under duress not to continue with police action at the time? The crime was reported, but the boy was never arrested/questioned as his father made me beg the police not to pursue the case. Any advice would be a huge help.