Prosecutor Agung Jayalantara told Fairfax Media the appeal to the High Court was because prosecutors had requested both Connor and her British DJ boyfriend David Taylor face the same sentence over the killing of Wayan Sudarsa, a father of two and member of the Bali police force for 35 years.

"This afternoon prosecutor Oka filed the notification to appeal to Denpasar District Court," he said.

However Mr Agung said prosecutors were unlikely to appeal Taylor's six year sentence.

The appeal is an ominous sign for Connor as it is common for appellate courts in Indonesia to impose harsher sentences on appeal.

Taylor, 34, and Connor, 46, were found guilty of fatal group assault in the Denpasar District Court on Monday and sentenced to six and four years' jail respectively.

Both punishments were light by Indonesian standards given an on-duty police officer had been killed and prosecutors had requested that both be sentenced to eight years' jail.

The maximum sentence for fatal group assault is 12 years.

Mr Sudarsa's widow, Ketut Arsini, said she wanted Connor to receive the maximum 12 year sentence over the killing of her husband of 31 years..

"If the prosecutor is appealing, then they believed four years is not enough punishment," she said.

"I myself, find it not enough, four years, not enough. If the law only allows a maximum 12 years, then I want her at least to be sentenced for the maximum, the full 12 years."

Connor's lawyer, Erwin Siregar, said he would also advise Connor on Monday morning to appeal.

"She's innocent, in my opinion she should appeal," he said.

"I will also advise her that prosecutors have decided to appeal, their reason to appeal is to get her to serve longer prison time. That would be my advice to her."

The judges rejected key elements of Connor's sentence including her claim that her only role in the police officer's death was to break up a fight between Mr Sudarsa and Taylor.

Judge Wayan Sukanila said Connor was not trying to separate Taylor and Mr Sudarsa when she sat on top of the police officer but was trying to help Taylor and prevent the victim from fighting back.

He was equally sceptical about her claims that she cut up Mr Sudarsa's cards in order to protect him from identity theft, saying she instead acted out of guilt.

"There is a disparity between the findings of the court, which were very damaging for Sara, and the relatively light penalty, which may not survive an appeal," Professor Tim Lindsey, the director of Melbourne University's Centre for Indonesian Law, Islam and Society, told Fairfax Media earlier this week.

Connor was ultimately given a lesser sentence than Taylor despite prosecutors requesting parity on the grounds Connor had given "convoluted statements" to the court and did not admit her guilt.

The judges took into her account that her two sons "still needed her very much" and she was separated from their father. They also said she was polite during the trial, had no criminal record in Indonesia and had offered to make a donation to Mr Sudarsa's widow, even though it was refused.

There are multiple precedents of foreigners having harsher sentences imposed as a result of appeals.

Heroin smugglers Scott Rush, Si Yi Chen, Matthew Norman and Tan Duc Thanh Nguyen, part of the Bali nine, had their sentences increased to the death penalty on appeal to the Supreme Court.

And convicted cannabis smuggler Schapelle Corby had her 15-year sentence increased to the original 20-year term when it was appealed in the Supreme Court.

Prosecutors have until March 27 to submit the full appeal documents to the Denpasar District Court.

"Our superior believes that since David and Sara were charged with the same crime and in the same capacity they should also serve the same time," Mr Agung said. "It is about a sense of fairness. That is why we are appealing."

The High Court appeal will be in the form of a written submission which will then be considered by judges.

It could take up to two months to process.

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