Mrs Crutchley was in the final stages of terminal stomach cancer, and died within hours of her son giving her an overdose of her drugs, which included painkillers and anti-anxiety medication.
During his trial, Crutchley told the court he never intended to kill his mother, only to relieve her suffering.
Mrs Crutchley was thrashing about in extreme pain and begging for help, the court was told.
Crutchley had the support of his family, who were stunned by the verdict.
His sister, Diane Millins, said she believed he was innocent and was in "an awful position" witnessing their mother suffering.
The Crown said Crutchley would have known his mother would have died following the increase in medication.
Shortly after the trial, Taumarunui community leaders called on the government to provide rural communities with better access to healthcare and improved resources, particularly for palliative care.
- NZPA