My friend recently found out about Uvisa, he was involved in an adult felony case where he was a victim in 2010. He pulled out a Register of Actions on the internet and can see his name on the subpoena. The criminal ended up in jail for a year. How are his chances of eligibility and success?

It all depends on luck now since one year time frame(I believe ) has passed. You can get all the certification from POLICE where the case was initially filed and all those affidavit and file it. No lost in trying. I would say go for it.

are you sure there is a 1 year time frame?

That is what I think(JUST THINK),, i may not be correct, like I said, there is no harm if you have valid reasoning.and you can gather the affidavit.

http://www.jessenlaw.com/us-immigration-u-visa.aspx
http://www.uscis.gov/sites/default/files/files/pressrelease/U-visaFS2_05Sept07.pdf

There is no 1 year restriction for filing U visa. You can file anytime if you meet these requirements. Four requirements:
1. The incident occured in US.
2. The crime falls under one of the specified categories ( google u visa eligible crime category)
3. Victim went through mental or physical harm.
4. Victim ready to help or has helped the government (state or federal) against the criminal.

If you can explain briefly about your case, I may be able to answer your other questions.
I'm not a lawyer. I'm suggesting as per my experience filing U visa.