Guessing it must be difficult at this late date to find anything definitive on CB giving a DNA sample or not.
Still, if CFS had CB's DNA, unable to see why a statement would be lacking in court that CB had been ruled out as the donor of the blood in the back EB's car. That would still leave CFS with the donor was a female offspring of Mr and Mrs B and much more definitive.
As it stands, it's 50 - 50 on who the donor was.
Cathy's trial transcript on examination by McMahon:
Q; Cathy, the kind of car elizabeth drove was what?
A; A Toyota Tercel
Q: On June 19th, or anytime in the three or four days after that, did you ever bleed in the back of her car at anytime.
A; No, I didn't
Q; Did you ever have a bulky object covered in your blood dragged into that vehicle
A; No
Q; Had you ever seen any blood in the back of Elizabeth's car.
A; No
That was all that I see mentioned about Cathy's blood on her exam or cross exam. There is no actual question as to if she gave or was asked to give a DNA sample.
Mr. B's trial exam by McMahon.
Q; I understand Mr B, as the investigation went on, the police asked you and Mrs B to go to a certain hospital in Scarborough, do you recall that
A; Yes sir I do, it was for DNA testing I believe
Q; You and Mrs B went to the hospital?
A; Yes, that's correct
Q; The purpose was for what? What did you give them at the hospital
A; They wanted a blood sample from my wife and I because we had four offspring and they wanted to guarantee the blood type, and the rest of it, is derived from us, and from the inside of the car
Q; Did you and Mrs B give a medical doctor samples of your blood?
A; We both did
Q; So there can be no confusion, from your marriage or your union with Mrs B you only had two female offspring?
A; That's correct
Q; Elizabeth and Cathy?
A; That's correct, Elizabeth and Cathy.
That's the extent of the blood and DNA from Mr B's trial exam and nothing from cross exam as far as I've read.
My opinion is that sister CB was never asked to give a DNA sample.
Hope this helps