A nurse is maintaining her innocence after prosecutors say she killed a friend who was reportedly distraught after a break-up and wanted to end his life by drug-assisted suicide.

Kristie Jane Koepplin pleaded not guilty in an Orange County court in California on Monday, two weeks after she was arrested in Arizona and extradited to California to face a felony murder charge in the death of Matthew Peter Sokalski.

Ms Koepplin, who is from Arizona, was released from custody on Monday after posting $1m (£772,000) bail but she cannot leave California or practice nursing as conditions of her release, according to Kimberly Edds, a spokeswoman for the Orange County District Attorney's Office.

The prosecution and defence each provided few details in the murky case and the criminal complaint remains under seal. Orange County officials did not immediately respond to The Washington Post's request for additional records, including the incident report and coroner's report for Sokalski's death.

On Monday, Todd Spitzer, the Orange County district attorney, alleged Ms Koepplin helped Sokalski die in April 2018 by injecting him with drugs.

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The Orange County Sheriff's Department opened an investigation into Sokalski's death after his body was discovered by a staff member of a hotel in Mission Viejo, California.

"California's right to die law strictly governs the conditions under which terminally ill adult patients with the capacity to make medical decisions can be prescribed an aid-in-dying medication," Mr Spitzer said in a statement.

"That was not the case here. It is beyond disturbing that someone who is trained as a nurse to aid the sick and the dying would twist their duty to willingly end the life of another human being."

Two months after Sokalski's death, a California appeals court reinstated the state's controversial right to die law, which allows terminally ill patients with fewer than six months to live to request lethal drugs.

Michael Guisti, Ms Koepplin's lawyer, denies wrongdoing by his client and disputes the prosecutor's allegation that Ms Koepplin was present at Sokalski's death.

"I don't believe she acquiesced to any request at all. If you look at the DA's press statement, there's a huge leap of faith - and almost nothing till we get to an assisted suicide accusation," Mr Guisti told The Post on Wednesday.

"In this case, especially since it has that 'angel of death' aura around it, people are paying attention, [but] my client just didn't do this."

A relative for Sokalski did not immediately respond to requests for comment.

Mr Guisti said Sokalski was "apparently heartbroken over some other woman - that's what we're understanding precipitated this thing".

He confirmed that Sokalski and Ms Koepplin had been friends for several years and credited Sokalski for introducing his client to her now-husband.

Ms Koepplin and her husband sold their home in California last year and moved to Peoria, according to her lawyer.

He said Ms Koepplin was aware that she had been under investigation for the past 16 months, but that her previous lawyer in Arizona told her that charges were unlikely; he said it was unclear why the DA's office was pursing Ms Koepplin now.

In criticising the Orange County DA's office for what he characterised as overly-aggressive prosecution "and a rush to judgment", Mr Guisti invoked his former client Michelle Hadley.

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Ms Hadley was framed and jailed for three months in a high-profile 2016 case in which Orange County prosecutors accused her of orchestrating an elaborate kidnapping and "rape fantasy" plot to endanger the woman who married her ex-fiancé.

She was later exonerated by the same office and prosecutors ultimately charged the wife of Ms Hadley's ex-fiancé with the scheme.

"We have a newly-elected DA, and he's not gonna let go of anything that has sizzle," Mr Guisti said.

A representative from Mr Spitzer's office declined to comment on further details of the case but said via email: "We only file cases if we can prove the facts beyond a reasonable doubt in a court of law."

Ms Koepplin faces up to 25 years to life in prison if convicted. Her trial is scheduled for January.