A woman and her partner have each been sentenced to 39 years in prison for the “horrific” murder of 15-year-old Sebastian Kalinowski.

Agnieszka Kalinowska, 36, and Andrzej Latoszewski, 38, were convicted at Leeds crown court in July of murdering Kalinowska’s son at their home in Huddersfield in a prolonged campaign of physical abuse amounting to torture.

Sebastian died after contracting sepsis, brought on by the injuries from hundreds of punches, kicks, whippings and stabbings over months.

Though they were not a whole-life term, the judge, Mrs Justice Lambert, said the sentence “may be the equivalent” as the pair would be in their late 70s when eligible for release.

Lambert also issued each of them a nine-year child cruelty sentence to run concurrently with their murder sentences.

Sentencing Latoszewski, she said: “There are times when it seemed to me that you had lost awareness that you were actually hitting a human being and not your punchbag.”

Video footage captured by cameras Latoszewski had installed in their home in order to control Sebastian showed prolonged beatings, with the teenager crying and screaming. Sebastian was also stabbed with a needle multiple times by Latoszewski and Kalinowska.

The boy was forced to do exercises such as push-ups and to sit facing the wall for hours.

The footage also captured Latoszewski, who used steroids, parading around the house and looking at himself in the mirror between assaults, while Kalinowska sat watching TV.

Other evidence shown to the court included text messages where Kalinowska asked Latoszewski to come back and “beat the shit” out of Sebastian. The pair also discussed how to torture him without leaving marks on his body.

He died of sepsis on 13 August 2021, caused by 23 rib fractures, after Kalinowska and Latoszewski waited two-and-a-half hours to call an ambulance after finding the boy unconscious.

The pathologist found 81 injuries on Sebastian’s body. Dr Michael Parsons said some of his injuries would normally be seen only in car crash victims.

The evidence in the trial was so distressing that jurors were discharged from jury service for life by the judge, who said their service had been “beyond the call of duty”.

After the sentencing, the lead investigator on the case, DCI Tony Nicholson of West Yorkshire police, described it as “without doubt the most harrowing case I have experienced in my 29 years as a police officer”.

He added: “Latoszewski and Kalinowska abused this boy in a manner which was wicked and evil, and we may never know why they chose to act in this inhuman way.”

Staff at Sebastian’s school described the teenager, who came to the UK in 2020 from Poland, as a “lovely boy” who was “shy”, “quiet” and “always pleasant.”