A murder mystery I’ll host at a bar

I’m hosting game night at my regular bar, and I’m gong to stage a murder mystery. Each of the suspect will make 4 statements, one of which is known to be a lie.

I tried to construct it as soundly as I could, using a grid to check each person’s lies and truths. I based it roughly on this other puzzle I found here:

Who is the thief? An elementary school teacher had her purse stolen

I just want to check that it’s interesting enough and that the logic checks out.

Kevin (the bar owner) is murdered, and there are four suspects. A partially-burned note is found in the garbage (I know, it’s just a game) that says “I know you paid to have Kevin killed, pay me or suffer the consequences”. The game is to identify the killer, the person who hired the murderer, and the blackmailer (revealing the last person as totally innocent).

Here are the four statements of all the suspects, can you solve it? I’d appreciate it if you could point out any logical errors and ways to improve or fix the puzzle, thanks.

1. Matt: I did not kill Kevin

2. Amy: I did not kill Kevin

3. Graham: I did not kill Kevin

4. Kristen: I did not kill Kevin

5. Matt: I’ve known Amy all my life, she’ll vouch for me

6. Amy: I don’t know what Matt’s talking about, I only met him a few months ago

7. Graham: Amy doesn’t know who did it

8. Kristen: Matt knows who did it

9. Matt: I’m totally innocent in all matters regarding this crime

10. Amy: Kristen knows I didn’t kill Kevin

11. Graham: Kristen knows who did it

12. Kristen: Matt killed Kevin

13. Matt: Graham killed Kevin

14. Amy: Kristen killed Kevin

15. Graham: Kristen is not the blackmailer

16. Kristen: Amy is the blackmailer

Thanks for your help!