'There's about a foot-and-a-half difference'

Former Australia captain Ricky Ponting has criticised what he believes are inconsistencies in cricket's ball-tracking technology following Mitchell Marsh's controversial dismissal at the WACA Ground.

Marsh was given out leg before wicket early on the final day of Australia's heavy first-Test defeat in Perth, sent on his way after South Africa successfully reviewed the not out decision from on-field umpire Aleem Dar.

Former Test skippers Michael Clarke and Mark Taylor both questioned the ball-tracking technology used as part of the Decision Review System in commentary with Nine’s Wide World of Sports, which showed the ball to be hitting leg stump.

Ponting, a member of the MCC's World Cricket Committee, agreed and claimed that the impact point plotted by the ball-tracking technology was incorrect.

And the 41-year-old said another review later in the day, where ball-tracking showed a delivery from Temba Bavuma to Nathan Lyon was missing the stumps by some margin, proved that Marsh had copped a wrong call.

"I think we've proven that on a lot of the replays we've seen that they've actually got that wrong," Ponting told BT Sport, before being backed up by co-commentators Michael Vaughan and Graeme Swann.

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"Even with a couple more of the decisions we've seen later in the day, (it) just goes to prove how far out that technology actually showed this one to be.

"(The Bavuma delivery) pitched about the same length away from the stumps (as the Rabada delivery), it's pitched on middle stump, which is where the other ball pitched, Rabada's has actually swung more, and there's about a foot-and-a-half difference there (with the ball-tracking)."

Ponting then added with a smile: "Or Rabada has bowled one that's gone both ways. That's why he's so good".

Ponting added that while he was a strong advocate of the DRS in general, it was crucial it was implemented correctly.

"I'm an advocate for technology in the game because I honestly believe we're getting more correct decisions now than we ever have because of the technology," he said.

"But if there is someone who's operating that system, they have to be experts in the game as well. Someone has missed something there (with the Marsh decision).

"If it's humans that are putting the infomation into the technology, then they have to see every single angle and make sure what they're putting in is absolutely spot on.

"Because not only could that be a big decision in the game, that could be (Marsh's) Test career as well, by the way."

Speaking after play, Australia captain Steve Smith also expressed his surprise at the Marsh decision.

"We're all about improvements and getting the game as good as it can (be)," Smith told Optus Sport’s Stumps.

"I was a little bit surprised by the Mitchell Marsh decision, that certainly looked like it was missing leg, Rabada must have started bowling leg-spin or something like that.

"That wasn't the way I saw it but I'm not the one who runs DRS."