The jury in a Launceston murder trial has been unable to reach a verdict after deliberating for five hours.

Jurors are trying to decide whether 52 year old Michael Vernon Lowe killed his ex-girlfriend's new partner at her Kings Meadows home last year.

37 year old Darren John Booth was stabbed three times after a violent struggle.

Lowe says he acted in self defence.

The jury will resume its deliberations on Monday.