Juror Theodora Dallas who carried out internet research at home while sitting at a criminal trial was jailed for six months for contempt of court today.
Academic Dallas, 34, had told other jurors what her research had revealed about a defendant on trial at Luton Crown Court in July 2011.
The judge aborted the trial after learning about her research.
She was sentenced today by three judges at the High Court in London, including Lord Judge, the Lord Chief Justice.
Dallas was present in court for the ruling.
She will serve three months and be on licence for the remainder of the term.
The judges refused Dr Dallas permission to appeal to the Supreme Court, but she can still apply directly to the highest court in the land.
Contempt proceedings had been launched against her by the Attorney General Dominic Grieve QC.
Lord Judge said Dr Dallas had "deliberately disobeyed" the trial judge's instructions not to search the internet and added: "The damage to the administration of justice is obvious."
Sentencing Dr Dallas, he said: "Misuse of the internet by a juror is always a most serious irregularity and an effective custodial sentence is virtually inevitable."
The judge said her counsel Charles Parry had made a plea to the court to be merciful and impose a suspended sentence.
Rejecting the plea, Lord Judge said there was "no sufficient basis" for suspension - "in this case an immediate custodial sentence is appropriate for the contempt which has been proved".
Lord Judge said Dallas was guilty of "contempt of the jury and the jury system", and the contempt had been proved "to the criminal standard".
He emphasised that jurors who attempted to "pick and choose" which principles governing trial by jury they would obey endangered the future of the jury system.
"In the long run, any system which allows itself to be treated with contempt faces extinction.
"That is a possibility we cannot countenance."
He said of Dallas, who came to England from Greece at the age of 19: "The defendant is a woman of positive good character and we acknowledge her achievements thus far in her relatively young life.
"We recognise she has now resigned from her appointment and has put her academic career in the long term into jeopardy."
But nothing had been said in mitigation that convinced the court she should be spared an immediate jail sentence.
At the time of the trial which she caused to be abandoned, Dallas was a psychology lecturer at the University of Bedfordshire, which has its main campus in Luton.
She told the judges she had "no intention" to "influence" the jury.
She had not "deliberately" ignored instructions but had "misunderstood" the trial judge's directions.
Mr Grieve, the Government's chief legal adviser, said the trial involved a defendant called Barry Medlock at Luton, accused of causing grievous bodily harm with intent.
He said jurors had been told by the trial judge to base decisions on the evidence and warned not to use the internet or discuss the case with others.
A juror had told an usher that Dallas had carried out internet research while jurors were deliberating their verdict.
Dallas had revealed to jurors that Medlock had previously been accused, and acquitted, of rape - information not given during the trial.
Mr Grieve said the judge had investigated and then aborted the trial.
Medlock had been re-tried in October, convicted and jailed, he said.
Dallas said she had been checking the meaning of grievous bodily harm on the internet.
She had added the word "Luton" to a search and that search had then produced a newspaper report which mentioned Medlock and the previous rape allegation.
Dallas said in a written witness statement given to judges that "sometimes my grasp of English is not that good".
"I did not understand that I could make no search on the internet," she said.
"I had no intention at all to prejudice the jury in any way. I had no intention to disobey what the judge said. I really apologise. I never thought it would cause such disruption."
Dallas, who told judges that one of her uncles was a sculptor who had designed the medals for the 2004 Athens Olympics, said she had resigned from her university post after facing disciplinary proceedings.
She had suffered depression and ill-health as a result of her ordeal.
Lord Judge said: "It is clear not merely that the defendant had indeed consulted the internet, and discussed Medlock's previous conviction and the fact that it involved an allegation of rape, but also that the remaining jurors were extremely disturbed, to put it no higher, by what they had been told.
"That, if we may say so, is greatly to their credit."
He added: "They were obviously concerned to ensure that their responsibilities as jurors was properly discharged.
"It also demonstrates that they had fully understood the prohibition against use of internet."
Lord Judge said the court had "no doubt" that Dallas knew "perfectly well" that the trial judge had directed her and the other members of the jury "in unequivocal terms" that they should not seek information about the case from the internet.
There was also no doubt that she "appreciated that this was an order" and that she "deliberately disobeyed the order".
He added: "By doing so, before she made any disclosure to her fellow jurors, she did not merely risk prejudice to the due administration of justice, but she caused prejudice to it.
"This was because she had sought to arm, and had armed herself, with information of possible relevance to the trial which, although not adduced in evidence, might have played its part in her verdict."
The fact that the jury was "rightly discharged" from returning a verdict, and a new trial ordered, meant that the "unfortunate complainant had to give evidence of his ordeal for a second occasion".
Lord Judge added: "The time of the other members of the jury was wasted and the public was put to additional unnecessary expense. The damage to the administration of justice is obvious."
In June 2011, a 40-year-old woman was given an eight-month jail term after becoming the first juror to be prosecuted for contempt of court for using the internet.
Joanne Fraill, 40, admitted using Facebook to exchange messages with Jamie Sewart, 34, a defendant already acquitted in an ongoing multimillion-pound drug trial in Manchester in 2010.
Fraill, from Blackley, Manchester, also admitted conducting an internet search into Sewart's boyfriend, Gary Knox, a co-defendant, while the jury was deliberating.
She was jailed after a hearing at the High Court in London before a panel of judges which included Lord Judge.
Passing sentence, Lord Judge said: "Her conduct in visiting the internet repeatedly was directly contrary to her oath as a juror."
end
Attorney General Mr Grieve told BBC Radio 4's World At One: "If a juror goes off and carries out research and obtains information that has never been put before the jury about the defendant then that is perfectly capable of influencing that juror.
"Nobody in court will have had the ability to deal with that information, explain it, challenge it or do anything about it.
"It is central to the fairness of our trial process that only what is heard in court should determine the jury's verdict."