Step One: What Do We Really Know?

Thanks for that post Tom! The reason I believe they had no defensive wounds is:

From Johnny's Autopsy:

The base of the long finger of the left hand shows dorsally a 3/4 inch
zone of bruising, and the hands otherwise show no evidence of trauma.

(All I see is a small bruise on the base of his middle finger?)

From Dana's Autopsy:

The hands are free of injury

Evidence of Review noted on review of case file 1986(? hard to read the date)

There were no defensive wounds found on Johnny Sharp or Dana Wingate but were several on Sue Sharp and she had blood on the bottoms of her feet indicating she had walked in blood.

From Sue's autopsy it doesn't appear she was beat in the face, or at least not enough to draw blood, until after she was gagged:(it appears to me that the blood on her face ran over her gag)

Considerable dried and some liquid blood is present over the entire face
in a sometimes smudged pattern. Blood appears to have extended downward
from the right side of the mouth and nose towards the posterior head and
neck.
The pattern stops abruptly on the face at the level of the gag mark,
and below the gag mark on the under surface of the chin is a very small
amount of patchy dried and somewhat smeared blood.

Just my opinion if Sue walked in Johnny or Dana's blood then it would appear she walked into the living room after Johnny and Dana were being beat/killed. So it doesn't appear that they came to her defense because it appears they were already down when she got to them. Yes, Sue definitely fought with someone.