Final answer:
The independent post-mortem examination requested by Matthew's parents would be considered a private autopsy, which is sought when family members wish for further investigation into the cause of death beyond what is determined by officials.
Step-by-step explanation:
The autopsy being requested by Matthew's next of kin after an inconclusive initial assessment by the coroner would be categorized as a private autopsy. This type of autopsy is not mandated by the state but is instead independently requested and funded by the family or next of kin for their own closure or to understand the cause of death better. Such autopsies are sometimes sought when the circumstances surrounding the death are unclear or when the family suspects that there may be more to learn about their loved one's passing.
Regardless of the fitness level or past medical history of an individual, sudden deaths like this are often assumed to be related to cardiac arrest, especially in the absence of other obvious causes. Cardiac arrest is a critical emergency where the heart fails to pump blood effectively, which can occur without warning even in seemingly healthy people. Private autopsies in these cases play a vital role in offering insights into conditions that may not have been previously diagnosed, contributing to an accurate determination of the cause of death.