Factual error: There is no way Laurel Lance would have been allowed on the prosecution team for Moira Queen's murder trial. Due to the facts that she both dated and as a lawyer represented the defendant's son, the defendant's daughter used to intern for her, and her boyfriend was one of the people killed in the Glades, it would have taken all of two seconds for the court to have her removed if she didn't willingly recuse herself, since her presence would be a major conflict of interest.
Factual error: In this episode Barry uses rat poison to save Oliver, from a poison that coagulated blood. Though rat poison contains anticoagulants like Warfarin, this is medically wrong because, It takes at least 1-3 days for Warfarin to be effective and it may even cause excess of coagulation during this time. It could never have saved Oliver instantaneously. What Oliver needed was heparin. So Barry in real world instead of curing Oliver might just have made him much worse.
Three Ghosts - S2-E9
Factual error: When Cyrus punches through the windshield of the truck, it shatters into hundreds of little pieces, like safety glass. Windshields are not made out of safety glass.
Suggested correction: When Diggle is walking away from Felicity, he is still talking to her but it looks like he is talking to Nyssa.
Stephen Edmonds 1
People have already tried to correct this mistake. It is valid. In the scenes prior, Nyssa says Oliver will do what it takes to kill her and Oliver says "tonight, Nyssa Al Ghul faces justice." Nyssa is there to bring the team the news that Oliver is going to try to kill her. Felicity says "Oliver wouldn't", meaning Oliver wouldn't try to kill Nyssa. Diggle says "I think what she's [she being Felicity] trying to say to say is that Oliver would never do anything to hurt you" [you being Nyssa whom Oliver is going to try to kill]. He is meant to say "Nyssa." Otherwise the entire line means Nyssa or Laurel are there to convince Felicity that Oliver would never do anything to hurt Felicity.
Bishop73