Hopefully this is not too upsetting but when we talk about fitting a body into a suitcase or similar thing we mustn't forget that rigor mortis starts fairly soon after death, about 3-4 hours, then moves slowly through the body from the head and neck downwards. After about 10 hours after death the whole body is stiff and remains so for 24 to 48 hours. So unless he moved her into a suitcase/bag within 3 hours of her death it would not have been possible. He either must have had a large enough suitcase/bag on hand or carried her in another fashion to the car, rolled up in something for example. If he had to buy a suitcase the next day it would have been too late.
It gives me the shivers to think about this