What do you mean even though I know Jack did it? If I knew he did it, that's hard evidence. And since when does likely=99.99%?
If you think you will ever get hard evidence out of a well calculated murder, no, I won't even go that far, an average murder plot, then you are dreaming. Apparently even having the perfect motive for a crime is not evidence.
Lets get even crazier. Say Jill is found shot dead with a bullet from Jack's gun. Isn't this not still circumstantial evidence? We still do not know what happened. We still have to use circumstantial logic to deduce that Jack shot her, since it was his gun, but we do not know that. There is still no evidence he shot her.