Almost one person with a disability is killed by their carer every three months in Australia.

For the first time, Background Briefing has calculated this number by reviewing years of court documents and media reports.

When a person with disabilities is killed, the burden of caring is often cited as a reason for the killing and may lead to lighter sentences.

Reporter Sarah Dingle investigates bias in the courtroom and asks the question: Does excusing carers who kill lead to a contagion effect?