Chandimal had been charged by the ICC for ball-tampering during the second Test in St Lucia after video evidence indicated that he applied saliva to the ball shortly after putting what the ICC has suggested was a sweet into his mouth. He pleaded not guilty to the charge, before attending the hearing where Srinath handed Chandimal the maximum punishment available under the code, which was two suspension points and a fine of 100% of his match fee.
The appeal is likely to hinge on what exactly Chandimal put in his mouth. One of the probable contentions is that Chandimal had had a number of things in his pocket during the day, including cough lozenges (which you cannot apply to the ball) but also almonds, and he does not remember which exactly of those things he put into his mouth in this particular clip.
This, the team feels, is different from the ICC's framing of Chandimal's defence. Upon suspending Chandimal for a Test, match referee Javagal Srinath had said in the ICC release: "Dinesh admitted to putting something in his mouth but couldn't remember what it was, which I found unconvincing as a defence and the fact remains it was an artificial substance." Chandimal's defence is likely to contend that there was no way the ICC could possibly know that it was a substance capable of altering the condition of the ball, because the video evidence does not make it clear what the substance was.
The argument, essentially, is that the ICC does not have sufficient evidence to find Chandimal guilty of tampering. This has been one of Sri Lanka's assertions from the beginning.