Police have arrested a 62-year-old Adelaide woman and will charge her with two counts of murder over the deaths of an elderly couple more than a year apart, saying she was a family member alleged to have administered drug overdoses.

Major Crime detectives arrested the woman, from Craigmore, on Tuesday morning over the alleged drug toxicity deaths of Brenda and Lynton Anderson.

Mrs Anderson, 94, died at Flinders Medical Centre, in Adelaide’s southern suburbs, in March 2022. Her husband, also 94, died in hospital after being found unresponsive at his Hackham home on May 1 this year.

South Australia Police last week launched a double murder investigation due to “similarities and abnormalities” in the toxicology results from both deaths, and revealed they had a suspect.

In a statement on Tuesday, police said it would be alleged that the elderly couple “died from drug overdoses after being deliberately administered medication” while Mrs Anderson was being treated as a patient at Noarlunga Hospital last year, and while Mr Anderson was at his Hackham home on April 30.

The arrested woman was refused police bail and is expected to be charged with two counts of murder later on Tuesday. She is expected to appear in the Adelaide Magistrates Court on Tuesday or Wednesday.

• This article first appeared in InDaily and is republished here with permission