A 26-year-old man has been jailed for 15 months after failing to seek medical help for his dying mother after she fell out of bed in the caravan they shared in the West Australian city of Geraldton.

Wilhelmina Pierce died in March 2011 after spending four days on the floor of the cluttered caravan.

During Corey Pierce's first trial, the court heard he had tried to lift his mother off the floor but could not move her because of the clutter.

Prosecutors said while the son did not intend to kill his mother, his failure to seek proper medical attention for her hastened her death.

The court was also told Mrs Pierce was a stubborn woman who had discharged herself from hospital against medical advice a month before her death.

The jury in the first trial was unable to reach a verdict in the case.

However, Pierce stood trial in the Perth District Court for a second time and was convicted of manslaughter by the jury last month.

In sentencing the 26-year-old today, District Court Judge Michael Bowden said Pierce was his mother's full-time carer and his failure to seek medical help led to his mother's death.

Pierce will be eligible for parole after serving half the sentence.