Man starts jail time for stabbing death

A Brisbane man has officially started his eight year jail sentence for fatally stabbing his ex-lover's father in the heart after threatening to slice him up.

Mitchell James Sayers pleaded guilty on Tuesday to the lesser offence of manslaughter, just two days into his murder trial for killing 54-year-old Ian Robert Jones.

The Brisbane Supreme Court heard Sayers went to Mr Jones' house on December 14, 2015 in a bid to find his one-time lover Jessica Haywood, who had broken up with him weeks earlier.

Sayers, then aged 28, sent hundreds of threatening texts to Ms Haywood and Mr Jones, including one just before the stabbing that said "I'm going to slice you up".

Mr Jones died shortly after being stabbed once in the chest, possibly with a letter opener.

Justice Martin Daubney said it was agreed Sayers had intentionally struck Mr Jones once with a knife but did not intend to kill him.

Sayers, who has already spent 20 months in custody, was sentenced to eight years imprisonment and will be eligible to apply for parole in 2021.