On two occasions in this Test Match, a catch has been referred, and in the process, whether or not the batsman got a touch has come into question. This is due to a subtle change in the ICC's Third Umpire Review regulations. See Appendix 4 here. (pdf)
The on-field umpire shall be entitled to refer an appeal for a caught decision to the third umpire in the following circumstances:
3.1 Clean Catches
a) Should the bowler’s end umpire be unable to decide whether or not a catch was taken cleanly, he shall first consult with the square leg umpire.
b) Should both umpires be unable to make a decision, they may consult by two-way radio with the third umpire. Following such consultation, the final decision will be made and given by the bowler’s end umpire, who will take into account the on-field umpires’ initial views and any other advice received from the third umpire.
c) The third umpire has to determine whether the batsman has been caught. However, when reviewing the television replay(s), if it is clear to the third umpire that the batsman did not hit the ball, he shall indicate that the batsman is not out. See also paragraph 6 below.
d) The final decision shall be indicated in the normal fashion by the bowler’s end umpire.
3.2 Bump Ball
a) Should the bowler’s end umpire be unable to decide whether a catch was taken from a bump ball or not, he shall first consult with the square leg umpire.
b) Should both on-field umpires be unable to make a decision, the bowler’s end umpire shall be entitled to refer the decision to the third umpire to review a TV replay(s) of the batsman’s stroke as in paragraph 2.2.
c) The third umpire has to determine whether the ball was a bump ball or not. However, when reviewing the television replay(s), if it is clear to the third umpire that the batsman did not hit the ball, he shall indicate that the batsmen is not out. See also paragraph 6 below.
d) The third umpire shall communicate his decision by the system as in paragraph 2.3.This provision has been in place (using almost exactly the same language) in the ICC's annual update of the Standard Test Match Playing Conditions since 2008-09, with the exception of the 2009-10 when DRS was mandatory in all Tests.
I wish they would add a third point which allows the TV Umpire to intervene if he conclusively finds the presence or absence of contact, based on the technology available in a given host country. That, in addition to these two clauses, would cover all eventualities for mistakes (i.e. a decision being made one way when conclusive evidence is available the other way) to be caught and corrected.
Some people say that this would cause the Umpires to check all the time. This is far from clear. The overwhelming majority of overs in a Test Match do not see players appealing for decisions.
With a couple of small tweaks, the current Third Umpire Review system could fulfill the ICC's ambition of getting rid of howlers altogether.