A dog owner who stabbed his pet then drowned her in a canal was convicted after the RSPCA's first bone marrow test was used in a prosecution.
Chester Magistrates' Court heard Brendan Murphy, who lives on a barge at Nantwich, anchored his dog Tara with a chain before throwing her in the water.
Murphy, 52, has been banned from keeping animals for 10 years and given a 10-week suspended sentence.
"It is upsetting to think about what she must have endured," said the RSPCA.
The charity was alerted after the decomposed body of the Japanese Akita was found floating in the Shropshire Union at Nantwich on 6 October 2018, with a chain attached to her abdomen.
A post-mortem test revealed the animal had been stabbed twice before entering the water alive, where she remained for about three weeks after perishing, the RSPCA said.
The vet also found Tara was suffering from a lung disease at the time of her death, which was left untreated.
The dog's microchip identified Murphy as the owner.
At first he claimed he had been unable to afford veterinary treatment and had buried his pet in woodland near Nantwich after she died on the barge, returning later to find the body disappeared, said the RSPCA.
But after the charity sent samples from the animal for forensic testing, canal algae present in the dog's bone marrow confirmed Tara died from drowning, the court heard.
The RSPCA said it used this technique, commonly employed by police, because the dog's body was so badly decomposed.
At the hearing on 11 November, Murphy was found guilty of three charges of causing unnecessary suffering to his dog by failing to provide veterinary treatment, as well as stabbing and drowning her.
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