Twin fingerprints are much beloved by scientists, who see them as a classic arena for the old nature-versus-nurture debate: What made you what you are today, your genes or your environment? Twin fingerprints clearly show that it’s a little of both. If you compare palm prints and fingerprints of the Dionne quintuplets (born in 1934, they were the first quints of which all five survived), you find that the broad-brush pattern of lines, whorls, loops, etc., as well as what researchers call “ridge count,” were quite similar for the whole crew. Nonetheless each kid had unique prints due to differences in detail. “There is as yet no evidence that the arrangement of the minutiae (ending ridges, bifurcating ridges, etc.) is in any way genetically influenced,” writes fingerprint expert James Cowger. Presumably these minor but crucial differences arise from random local events during fetal development…
But as I understand, the key points in fingerprint ID are the points where lines, meet, or dead end, and their relation to each other. What form the pattern takes is relevant in establishing “yes, the are both whorls” or such, but the main thing is where those particular line point characteristics are.
So therefore, a set of 9 prints is not likely to have any details on whether the missing finger would match a crime scene, except maybe to predict the pattern - which is what, 1 in 3?
So if the fingerprints of identical twins are not identical, but are often similar…
Q: Are they sufficiently similar that a forensic scientist looking at the fingerprints of innocent twin A (in custody as a suspect) and finding them different-from-but-similar-to the crime scene evidence, might see sufficient similarity so as to posit the existence of evil twin B, who needs to be apprehended for questioning?
(That is, without prior knowledge that there even exists a twin B)