During the trial, when Atticus is questioning Tom Robinson, Mr. Link Deas interrupts the proceedings to vouch for Tom's character, after which Judge Taylor kicks him out of the court room. Deas is known to have hired other black workers and he hires Helen after Tom is killed.
“I just want the whole lot of you to know one thing right now. That boy’s worked for me eight years an‘ I ain’t had a speck o’trouble outa him. Not a speck."
In Chapter 30, after Bob Ewell is killed during his attack on Jem and Scout, Atticus and Heck Tate discuss what transpired during the attack. Tate wants to spare Boo Radley any more exposure in the public eye and he also sees Ewell's murder as a justifiable crime. Although this is clearly after Tom is dead, Tate does speak out on Tom's behalf in this conversation with Atticus. He is determined to frame the story that Bob Ewell fell on his own knife. He is so determined because this will save Boo from being drug "into the limelight." Tate also indicates that Bob is responsible for Tom's death.
There’s a black boy dead for no reason, and the man responsible for it’s dead. Let the dead bury the dead this time, Mr. Finch. Let the dead bury the dead.
If Tom is "dead for no reason," it stands to reason that Tate believes Tom was innocent.
Mr Underwood, the editor ofThe Maycomb Tribune, also stood up for Tom Robinson in his editorial. Scout recalls "Mr Underwood was at his most bitter" (p265) and went on to say "Mr Underwood simply figured it was a sin to kill cripples, be they standing, sitiing, or escaping. He likened Tom's death to the senseless slaughter of songbirds by hunters and children....." (p265). Therefore, the mockingbird (aka Tom) was senselessly slaughtered by the hunters and children (racist residents of Maycomb).
I have no doubt that Mr Underwood tried to make the residents realise what they had done to an innocent man.