De Goey threw himself at the mercy of the AFL tribunal on Tuesday night, pleading guilty to the rough conduct charge and telling the three-member jury how remorseful he was.
Opinion had been split as to whether De Goey should receive a three, four, or five-week ban for the bump.
Eagles midfielder Dom Sheed went as far as saying De Goey should be rubbed out for one or two months, before later apologising for that comment.
AFL counsel Andrew Woods pushed for a four-week suspension, saying the vicious nature of the hit and the fact it caused a concussion meant it didn't warrant the minimum three-week ban.
The three-person jury of chairman Jeff Gleeson, Jordan Bannister and Stewart Loewe deliberated for 27 minutes before settling on three weeks.
It means De Goey will miss matches against Melbourne, Adelaide and Gold Coast before returning for the round 17 clash with the Western Bulldogs.
During evidence, De Goey said he regretted the bump straight away.
"I don't go out there to play my footy in a dirty way," he said.
"To see someone get injured like that is disappointing. I wanted to make sure his wellbeing was OK.
"Directly after the game I followed up with (Eagles veteran) Shannon Hurn to ask if Elijah was on the bench so I could give him a verbal apology.
"Unfortunately he went down to the rooms ... so I proceeded to send him an apology text message. He was appreciative of the message."
Woods used Adelaide forward Shane McAdam's bump on GWS defender Jacob Wehr from earlier this year as part of his push for a four-match ban for De Goey.
McAdam received a three-match ban for that hit, but Woods pointed out it didn't result in a concussion.
"Here (with De Goey) we have a similar action with a serious injury, being concussion," Woods said.
"The amount of force deployed on Hewett - that puts this at more than that three-week entry level sanction.
"The player turns, flexes, raises his shoulder, positions his body sideways, leaves the ground briefly - all in the name of increasing impact.
"Looking at that footage, it could have involved a broken jaw or other broken bones in the head. There was potential for even more injury."
Stephen Russell, acting on De Goey's behalf, said a three-week penalty would be fair, citing the Magpie star's remorse and decision to plead guilty at the earliest chance.
He also said De Goey's bump was a split-second decision after Hewett had fired off a handball.
"The player struck by McAdam (in that other example) was standing still. In this incident, the major part of the momentum is coming from Elijah," Russell said.
"Your opportunity to even get out of the way is limited.
"He (De Goey) has chosen to provide a hip and shoulder. He's done it incorrectly.
"But applying a hip and shoulder is still within the rules. It has gone badly wrong, and that's why he pleads guilty to the charge.
"It's been done at the very earliest opportunity and it's a clear show of remorse."
