Mathis is innocent.He always has been.
QoS adresses a question I had about Casino Royale ,who paints Mathis as Le Chiffre's leak.
If Mathis' intention was to kill Bond,why wait until he's concious and coherent to poison him with a drink?
Granted Bond is in a wheelchair,but a former SAS soldier is still plenty deadly with his hands.
Since the movie establishes Vesper and Mathis being present while Bond was passed out,that would have been a MUCH better time for Mathis to poison him via IV in his hospital bed while he's drugged to unconciousness instead of waiting X amount of days for Bond to be released to a wheelchair,then mixing the poison in his presence and asking him to drink it.
Second,Vesper says 'Mathis needs me' before she stages her kidnapping by Le Chiffre.Who coincidentally utters the line about Mathis being 'his' special friend.
This he said so that Bond wouldn't put two and two and suspect Vesper,who Le Chiffre still needed to matter to Bond so as to coerce the password out of Bond via Le Chiffre 'torturing' Vesper.
When of course Vesper was in on the whole hustle.
This also adresses why Vesper walks off the ship alive when the rest of Le Chiffre's entourage ate lead courtesy of Mr White.