The first juror to be prosecuted for contempt of court for using the internet has been sentenced to eight months in jail.

Joanne Fraill, 40, admitted at London's high court using Facebook to exchange messages with Jamie Sewart, 34, a defendant already acquitted in a multimillion-pound drug trial in Manchester last year.

Fraill, from Blackley, Manchester, also admitted conducting an internet search into Sewart's boyfriend, Gary Knox, a co-defendant, while the jury was still deliberating.

Sewart was given a two-month sentence suspended for two years after also being found guilty of contempt.

When the lord chief justice, Lord Judge, announced her eight-month sentence, Fraill said "eight months!" and put her head on the table in front of her and cried.

Fraill, a mother of three with three stepchildren, sobbed uncontrollably with her head in her arms, and the judge announced a short adjournment "for everyone to calm down".

Sentencing Fraill, the judge said in a written ruling: "Her conduct in visiting the internet repeatedly was directly contrary to her oath as a juror, and her contact with the acquitted defendant, as well as her repeated searches on the internet, constituted flagrant breaches of the orders made by the judge for the proper conduct of the trial."

Later Sewart said: "I really feel for the woman [Fraill]. She's got kids. She apologised and she's not a bad lady. I really feel for her."

Fraill hugged relatives, who were also crying, before she was led away to start her sentence.

Knox, Sewart's 35-year-old partner, is applying for his conviction to be overturned on the basis of alleged jury misconduct. He was jailed for six years after being found guilty of paying a police officer to disclose information on drug dealers.

Fraill and Sewart were found guilty of contempt at the high court on Tuesday, in a case heard by the lord chief justice, sitting with Mr Justice Ouseley and Mr Justice Holroyde.

Fraill admitted emailing Sewart while the jury was still deliberating in the drugs trail in August last year because she felt "empathetic" and saw "considerable parallels" between their lives.

Sewart, who was acquitted at the trial in Manchester, admitted knowing that Fraill was a juror in the trial when she added her as a Facebook friend during jury deliberations. Sewart asked her in a Facebook chat on 3 August "what's happenin with the other charge??", to which Fraill responded by asking her to clarify her question.

Fraill then wrote: "cant get anyone to go either no one budging pleeeeeese don't say anything cause jamie they could all miss trial and I will get 4cked to0."

The lord chief justice, discussing the reasons for the sentence in the high court, acknowledged that Fraill was "a woman of good character" and was not involved in an attempt to pervert the course of justice. But "misuse of the internet by a juror" was always "a most serious irregularity and contempt".

He warned that a custodial sentence for any juror committing similar contempts "is virtually inevitable".

He added: "The sentence is intended to ensure the continuing integrity of trial by jury."

He said of Fraill: "Throughout, she was acting on her own initiative, without any oblique motive, and there is no evidence to suggest that she used her searches on the internet in order to exert improper influence on the verdicts of the jury.

"Without in any way condoning her actions in contacting Sewart after Sewart's acquittal, we carried out an examination of the psychiatric evidence to understand how her own background may have led her to wish to commiserate with Sewart's personal problems arising from the fact that a 14-month period in custody had separated her from her baby."

But the text of the communications between them "went much further than the expression of a compassionate concern".

When the question of her Facebook contact was raised with her in the crown court, "this woman of good character immediately and unhesitatingly admitted what she had done and apologised for it". She then went on to provide evidence against herself of her misuse of the internet throughout the trial, said the judge.

The solicitor general, Edward Garnier QC, said: "The lord chief justice could not have been clearer.

"Joanne Fraill and Jamie Sewart's conduct was a clear contempt of court. Jurors should take careful note and know that the law officers will prosecute those who commit contempt."

He added: "Both of these women were well aware that they should not have been engaging in this discussion.

"The jury system is a cornerstone of our society and confidence in this vital part of our criminal justice system will crumble if jurors do not take their responsibilities seriously.

"Long before social networks, the courts have been in no doubt that discussions inside the jury room must stay there. The internet doesn't make judges' warnings not to talk about a case or research it any less important."