The 26-year-old Northampton captain, who has won 39 caps for his country, faces a disciplinary hearing after being accused of biting the finger of Ireland flanker Stephen Ferris during England's 30-9 Six Nations victory on March 17.
The offence carries a low-end entry point of a 12-week suspension, which would put Hartley's participation in England's summer tour in doubt.
The mid-range punishment for biting is 18 weeks while there is a ban of 24-plus weeks at the top end in the International Rugby Board's disciplinary sanctions table.
The maximum sanction is a four-year punishment.
Hartley, who was born in New Zealand but qualified for Red Rose duty through his English-born mother, served a 26-week ban for gouging in 2007 after being cited for making contact with the eye area of Wasps players Jonny O'Connor, James Haskell and Joe Worsley during a Premiership fixture.
Hartley pleaded not guilty on all three counts, but a Rugby Football Union disciplinary panel found him guilty in relation to the offences against Haskell and O'Connor, but he was cleared on the Worsley charge.
The incident with Ferris occurred during the 28th minute of England's comfortable Twickenham win, which saw them secure second place in the Six Nations table after an encouraging campaign under interim coach Stuart Lancaster.
Television footage did not capture the alleged incident but Ferris and some of his team-mates complained to Welsh referee Nigel Owens in the immediate aftermath.
Owens said he had not seen anything but told captains Chris Robshaw and Rory Best: "I have an accusation of biting, a clear mark on the finger.
"I did not see something. If I do it will be dealt with severely, which would be a red card.
"It could be dealt with afterwards. If it is seen it will be dealt with. I did not see it.
"Have a word. Nothing like that takes place in this game. I can only deal with what I see. Have a word please.
"I have had a look. Unless I can see it, it's been dealt with, OK?"
Owens then spoke to Ferris while the Ulster forward received treatment, saying: "I have done all I can. It has been noted. If I don't see it I can't do nothing about it. It has been spoken about and dealt with."
The charge of an act "contrary to good sportsmanship" against Hartley was brought by the Italian citing commissioner Alberto Recaldini after reviewing footage.
But Recaldini incorrectly documented that the incident took place in the 23rd minute, when it fact it occurred in the 28th minute.
It is understood Recaldini has acknowledged the mistake in his report.
The chances of Hartley's legal team successfully using the mistake as a loophole to have the case dismissed have reduced significantly following an incident on England's tour to Australia in 2010.
On that occasion lock Dave Attwood was cited for incidents of alleged stamping in a game against the Australian Barbarians, but he was cleared without a hearing as the citing commissioner was Australian, and therefore deemed to not be independent.
A clause is now in place under the International Rugby Board's regulation 17 that allows the chairman of a disciplinary committee to note an inaccuracy of that nature, but to still proceed to dealing with the alleged act of foul play.