The lineups were egregiously unfair and biased, and thus unreliable as evidence. Many of the "identifications" weren't even lineups.
And let's get real. The chances that every witness at a fair line up selects the same person are minimal.
Take the Davis girls, for example. They heard shots and ran to their front door. Given the distance the shooter had to run from Tippit's car to their front door is minimal, it's amazing just how quickly those girls must have reached the front door, but that aside. They said that when they arrived they saw a man running through their front garden and past the front door. Now how long - be honest - did it take the shooter to pass their front door? Three seconds, four or five?
So, we are asked to believe that two girls who only saw a guy running past their front door for a few seconds, managed to both identify that man hours later during a line up? Really?
Their powers of observation must be phenomenally out of this world!