Whose profile matched the bloodstain on suspect D's jeans?

Referring to the case of 3 Individuals are found in a car crash and fire.

I believe the answer is victim 3

Criminologist usually use uses a fluorescent chemical called luminol in order to display left-over blood that are tainted in carpet or clothes.

After that, the Criminologist could compare the blood in the crime scene to the blood from the actual body of the victim for comparison.