Why does Roderick want to wait before they bury Madeline?

It was Madeline's final request before she died.
A fortnight is the traditional wait time for mourning.
She can't be buried until the spring when the ground thaws.
Due to the unusual nature of her death, and the obtrusive requests of her doctors to investigate.

Due to the unusual and mysterious circumstances of Madeline's death, Roderick wants to wait before burying her in order to confirm that she is truly dead and not just in a paralyzed state. The doctors have also requested to investigate her death and Roderick wants to allow them the time and space to do so before laying Madeline to rest.