The stab wounds themselves could actually be evidence if they can match (or closely match) a knife. And the location of the wounds might be telling of someone with training and/or on offense or defense. If the knife had the serrated top edge (like a combat knife), it would leave some tell tale wounds.
That said, the evidence would be circumstantial unless they matched DNA to the Soldiers equipment or visa versa.
Given the prior physical contact between the two people involved, they would have to find the knife with both of their DNA on it, otherwise any DNA transfer at all would be blown out of the water by the defense based on that earlier contact.