Three goals in a four-minute burst from Harry McKay had dragged the Blues back into Thursday night's contest and Newnes' snap shot appeared to have trimmed the margin to three points.
But it was ruled touched on review and the Tigers booted a steadying goal through Shane Edwards less than a minute later.
Richmond hung on for a 15-point victory, with the result costing the Blues (9-4) a share of top spot with Brisbane, Melbourne and Fremantle.
In his post-match assessment, Voss said he wasn't convinced the Newnes shot was touched by the Richmond defender.
"Make up your own mind. I think it's got to be definitive, doesn't it?" Voss said.
"If we're going to make decisions like that in games, you'd hope it's definitive.
"I guess I've now got the luxury of being able to sit back and see it and make my own judgement with it slowed down a little bit.
"But certainly we'd want to make sure we're absolutely 100 per cent sure before overturning something like that.
"Clearly, the call was made and we've got to end up living with the result."
Voss added he didn't think there was enough evidence to overturn the decision.
"It didn't look it from where I was but I don't watch the 10 different angles of it," Voss said.
"I've got one and looked at it and if it was touched then we move on."
Richmond coach Damien Hardwick last month called on the AFL to fix the review system, suggesting it takes too long, but laughed off Thursday night's crucial decision.
"They were good tonight, weren't they?" Hardwick said.
"We do (get footage in the coaches' box) but we don't know the umpire's call ... it's challenging but at the end of the day there's not much we can do about it."
Already undermanned, Carlton suffered further injury blows when Jack Martin (tight calf) and mid-season draftee Sam Durdin (knee) failed to see out the match.
Durdin was making his club debut after being recruited to fill the gaping holes left in defence by injured talls Jacob Weitering, Mitch McGovern and Oscar McDonald.
The Blues take on Fremantle at Marvel Stadium next week as the finals race heats up.