Joe Root's controversial dismissal had to stand because there was no firm evidence that it should be overturned, says Michael Atherton.
Root immediately called for a review after being given out by umpire Marais Erasmus, who adjudged him caught behind off Shane Watson.
But third umpire Tony Hill decided that DRS did not provide a compelling case for him to reverse the initial decision and Root had to go having made four off 16 balls, leaving England - at one stage 85-0 - wobbling on 90-2. By stumps the tourists were 180-4 in reply to Australia's 385.
Reflecting on Root's downfall, Atherton said: "Under the protocols as they stand, I thought the correct decision was made given that the on-field umpire gave it out.
"There was conflicting evidence from the technology. There was definitely a sound as the ball passed the bat; the bat was nowhere near the pad but there was definitely a sound. There was nothing on Hotspot but there was a little something on Snicko.
"So given that conflicting evidence, the third umpire did what he could only do which is say we'll stick with the on-field umpire's decision.
"Clearly Joe Root did not think he was out. He was absolutely distraught as he walked off the field. He reviewed the decision straight away. He didn't even consult Cook at the other end. So there was no doubt his mind that he hadn't hit the ball.
"Equally, the appeal from Australia was pretty convincing as well. In the end I think the right sort of protocol was followed and the on-field umpire's decision stood."
Australia began the day on 326-6 and lost three wickets for 28 runs before last pair Peter Siddle and Nathan Lyon frustrated England with a 31-run stand that spanned 7.4 overs.
In the Sky Sports commentary box, Sir Ian Botham and Nasser Hussain criticised captain Alastair Cook for not setting attacking fields.
Atherton agreed but said experienced seamers James Anderson and Stuart Broad should share some of the blame.
"They didn't have enough slips in place but you can't just focus on Alastair Cook - you've got two bowlers there with 562 Test wickets between them. They can ask for more slips as well.
"The key thing here at Perth is that you are going for runs - it is a fast-scoring ground. The pitch and the outfield are quick.
"The majority of catches come in that arc between wicketkeeper and gully, so what you have to try and do as a captain - and it's not easy when the ball is flying around at over four runs an over - is hold your nerve and have as many catchers as possible in that arc.
"This morning you had Broad and Anderson with a ball that was about 10 overs old bowling at Siddle and Harris, two tail-enders, and England should have had more slips in place."
Our pundits' view on Root's dismissal...
SIR IAN BOTHAM: It looked to me like the ball got past the edge of the bat. There was nothing there on Hotspot but Snicko said there was a little noise. The decision was upheld and while Joe Root was not happy, if the umpire has made the decision on the field, there's no evidence to say he got it wrong. The Australians all went up together. The umpire did take his time but he's entitled to do that. There was nothing there that said to me that you have to reverse that decision.
ANDREW STRAUSS: The dismissal was a tough one because there was definitely a noise as the ball passed Root's bat and there wasn't conclusive evidence to overturn the decision. It's another one of those situations where the technology looks a little bit confusing. The Australians went up very loudly, there was a noise and Root's bat wasn't near his pad. My gut feeling is that there was a tiny feather on it.
DAVID LLOYD: Joe Root didn't think he was out - he was adamant about that - but you can understand the appeal and the decision, because there is a noise and it all looked in sync. Root reviewed it immediately, so he told us straight away that he's not hit it. But is there enough evidence there for the third umpire to say that this is a very poor decision from the on-field umpire and I'm going to turn it around? What intrigues me is real-time Snicko which, as I understand it, should give a very definite indication that a batsman has hit the ball. But on the graphic there is just a tremor. There's nothing much there. Is that enough to say he's nicked it?
SHANE WARNE: Root was given out on the field so the evidence has to be 100 per cent clear for the umpire to overturn the decision. There is a noise there and the bat is away from the front pad. Joe Root might be a very, very good actor but his natural instinct was 'I didn't hit that, I'm referring it'. If you asked the third umpire from scratch 'is this out' I think he'd probably say 'I'm not sure so I'll have to give the benefit to the batsman' but in his current role there has to be clear evidence for him to overturn it and I'm not sure it was 100 per cent crystal clear for him to say 'you know what, he hasn't hit that'.
Watch highlights of today's play throughout the day on Sky Sports 2, starting at 11.30am, and On Demand from 6.30pm. The Ashes Verdict is on at the earlier time of 12.30pm and our live coverage of day three gets underway at 2.25am.