Murphy's goals on Monday (Tuesday AEST) were a major talking point, as was the second-half appearance of Jeremy Monga, who at 15 years and 271 days became the second youngest player to appear in the Premier League.
Monga replaced Bilal El Khannouss for Leicester 16 minutes from time wearing a different, logo-less shirt from his teammates because he is too young to advertise the betting firm that sponsors the home side.
Murphy scored the opener after two minutes when he stole in at the back post to convert a low cross from Tino Livramento.
Leicester had six men inside the six-yard box, but the ball went past them all and Murphy made no mistake.
The well-travelled winger scored a breathtaking second nine minutes later, thanks largely to the audacity of Fabian Schar.
Schar's attempt from inside his own half bounced back off the crossbar with goalkeeper Mads Hermansen well beaten, but Murphy followed up to slam home the rebound with the Leicester defence AWOL.
Former Leicester winger Harvey Barnes scored the third after 33 minutes when he poked home a Joelinton shot that the keeper parried.
It was a damage limitation exercise from then on for Leicester, who became the first league team to lose eight consecutive home matches without scoring. They remained second to last, three points behind Ipswich and five behind Wolves.
"It's hard to describe, to be honest, with how it's been, and it makes us feel awful right at the moment," Leicester defender James Justin said.
"You feel disconnection and disappointment when you step off the pitch ... it's not been good enough for a couple of months now.''
Newcastle moved into fifth place, equal on points with Chelsea.
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