In case of deaths due to asphyxia, the part which should be dissected last is -
In cases of death due to asphyxia, especially in hanging and strangulation, neck should be opened last, so as to provide a clear field devoid of blood during dissection thus avoiding artificial hemorrhages.
In these cases, skull is opened first and brain is taken out to drain out the blood from neck. And chest organ is removed prior to neck dissection to avoid injuries to neck veins.
Neck
Thorax
Abdomen
Skull