Smartwatch data proves Australian woman killed mother-in-law, prosecutors say

Caroline Nilsson, left, is accused of beating Myrna Nilsson to death in their Adelaide home in September 2016. (Facebook)

A South Australian woman charged with murdering her mother-in-law has sobbed through a court appearance in Adelaide where prosecutors outlined how recovered smartwatch data will be used as key evidence against her.

Caroline Nilsson has been charged with the bashing murder of Myrna Nilsson, 57, at their Adelaide home in September 2016.

At the time of the incident, the 26-year-old told police that her mother-in-law had been attacked by a group of men who had forced their way into the property after a road rage incident.

About three hours after the reported home invasion, she was found in the street by neighbours with her hands and face bound with tape.

But prosecutor Carmen Matteo told Adelaide Magistrates Court on Thursday that it was the crown case that the story Ms Nilsson had concocted was demonstrably false and the home invasion crime scene had been fabricated.

Ms Matteo said a forensics expert had analysed the dead woman’s smartwatch and had narrowed the time from when she was attacked to when she died to a seven-minute window.

She said the data showed a burst of heavy activity, consistent with the woman being the victim of an "ambush-type" attack followed by a period of less activity when she possibly lost consciousness.

Ms Matteo said the watch stopped recording the woman’s heart rate soon after.

"The prosecution accumulates those timings and the information about energy levels, movement, heart rate, to lead to a conclusion that the deceased must have been attacked at around 6:38pm and had certainly died by 6:45pm," she said.

The prosecutor said if those timings were accepted then it contradicted statements from the accused that her mother-in-law had been involved in an argument with her attackers for about 20 minutes.

Defense counsel Mark Twiggs said his client would deny the offending with her case to return to court on June 13.