New Delhi: On the fourth day of the second Test being played between India and England Akash Deep bowled England batsman Joe Root for just 6 runs in the second innings and sent him to the pavilion. This wicket was considered the turning point of the match but now a controversy has arisen over it. Commentator Alison Mitchell believes that this ball was a back-foot no-ball and should have been declared invalid. Commentator Alison Mitchells claim Alison Mitchell who was commentating on BBC Test Match Special (BBC TMS) commented long after the bowling that Akash Deeps ball which got Root out could have been a no-ball. He said At the time of ball release Akash Deeps back foot was about two inches outside the line of the return crease. The ball should not have been considered valid but it was not caught. What does the back-foot no-ball rule say? According to MCC rule 21.5 of cricket for a valid delivery the bowlers back foot must be within the line of the return crease determined by his bowling style and must not even touch the line. If the bowlers back foot goes outside the return crease it is considered a back-foot no-ball even if the front foot is in the correct position. Is this the first time it has happened? Back-foot no-ball incidents are rarely seen in cricket as most umpires focus only on the front-foot. However it is clear in the rule that the back foot should also be within the crease. Interestingly sometimes the front foot goes outside the return crease like Ravichandran Ashwin once did in the IPL while bowling against Rajasthan Royals but it was legal under the rule. Did the umpires commit error? In this case the umpires considered the ball legal and Joe Root was given out. But if Mitchells claim is true it was a technical lapse which should have been stopped by the on-field or third umpire. In such a situation the question arises whether enough attention is being paid to back-foot no-balls? Will it affect the result of the match? Even if it was a technical lapse until the umpires take any action the wicket will be considered valid. England still need 536 runs to win and they are at 72/3. In such a situation this controversy may become a topic of discussion but at the moment it does not seem to have a direct impact on the result.