A family member has been charged with two counts of murder over the deaths of an elderly Adelaide couple who police say overdosed on deliberately administered medication.
Brenda Anderson, 94, died in hospital in March last year.
Her husband Lynton, also 94, died after being found unconscious by a carer at his home in May this year.
Police allege both died from drug overdoses from intentionally administered medication.
Last week, Detective Inspector Mark McEachern said concerns over Mrs Anderson's death were first raised during a coronial investigation, which unearthed alarming toxicology results.
A similarly concerning toxicology report was returned after Mr Anderson's death.
"The toxicology in both people was quite similar in so far as raising our suspicion that the medication that was in there should not have been in there," Insp McEachern said.
Detectives had no concern with the level of care Mrs Anderson received while in hospital.
However, when any innocent explanation for the toxicology abnormality was eliminated, the possibility of a deliberate act by another party became the focus of the investigation.
Police believed Mrs Anderson was killed by a person known to her and in a close enough relationship to have been visiting her in hospital.
Detectives had also ruled out carers being involved in Mr Anderson's death.
On Tuesday, police said a 62-year-old woman, who was a family member, had been arrested and later confirmed she had been charged with two counts of murder.
Police previously asked to speak to anyone who had contact with the couple, particularly those with knowledge of any prescription or non-prescription medication they were taking.
They said they had been working with the couple's broader family, who had been shocked by the forensic findings.
