The confusing complexities of the Decision Review System (DRS) were on display again on Saturday morning when Australia opener Chris Rogers successfully overturned a caught-behind decision.u00a0Following an Ashes series in which DRS has become a major talking point, Press Association Sport&rsquo;s Matt Somerford details some of the key points the officials are obliged to adhere to when forming a decision. <img alt="Aleem Dar" src="http://images.mid-day.com/2013/aug/Aleem-Dar.jpg" style="width: 500px; height: 319px;" /> Umpire Aleem Dar explains the third umpire&rsquo;s decision to give Chris Rogers (left) not out on Saturday. What is Hawk-Eye and how is it applied? Hawk-Eye is the ball-tracking technology used for lbw decisions. Based on the path of the ball it determines if it was likely to continue on to hit the stumps after contact with the pad. There is a small margin of error in the system, however, meaning not every decision it determines will hit the stumps is given out lbw. This is when &lsquo;Umpire&#39;s Call&rsquo; appears on our television screens. What is &lsquo;Umpire&rsquo;s Call&rsquo; and how is it determined? The DRS will defer a decision back to the on-field umpire when it is unable to conclusively prove whether a batsman is in or out.u00a0Most often this will happen with lbw decisions when Hawk-Eye&rsquo;s margin for error is factored into decision-making. To accommodate this the ICC has ruled that if Hawk-Eye suggests the ball would only hit the outer half of the stump or bail - or pitch fractionally outside leg stump - then a definitive answer is not certain and therefore the &lsquo;Umpire&rsquo;s Call&rsquo;, whether out or not out, remains. <img alt="Chris Rogers" src="http://images.mid-day.com/2013/aug/Chris-Rogers.jpg" style="width: 500px; height: 602px;" /> Chris Rogers. Pics/Getty Images If the Rogers&rsquo; decision was &lsquo;Umpire&#39;s Call&rsquo; then why was he not out? The Rogers referral was a rare instance when &lsquo;Umpire&#39;s Call&rsquo; resulted in a different outcome to the on-field signal. Tony Hill gave Rogers out caught behind before the DRS showed he did not hit the ball. DRS can still look for other modes of dismissal and determined that an lbw review would return a verdict of &lsquo;Umpire&rsquo;s Call&rsquo;.u00a0Rogers therefore remained because the umpire had not given him out lbw - indeed he thought Rogers had hit the ball. Would DRS have given Rogers out if Hawk-Eye showed the ball would&rsquo;ve hit middle stump, halfway up? Yes. Once reviewed, if Hawk-Eye can definitively prove a batsman is lbw it does not matter what the on-field umpire&rsquo;s original decision was. Why is Hot Spot not working effectively in this Ashes series? That is the question of the summer and a point Hot Spot inventor Warren Brennan has admitted is of personal concern.u00a0The ICC have pointed out that, like Hawk-Eye, Hot Spot is not a definitive guide and that it is used only as means to help the third umpire make a decision. Brennan has suggested the coverings used on bats are serving to hide faint edges and today called for them to be removed.

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All you wanted to know about DRS

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