Compare characters and show who was more effective. More in description

Compare Romaine Heilger’s appearance as a witness for the prosecution in Leonard Vole’s case with the bartender Paquette’s appearance as a witness for the prosecution in Lt. Manion’s case in Anatomy of a Murder. Both of these witnesses ended up intentionally helping the cases for the defense in part because of their roles as prosecution (rather than defense) witnesses. Which of these two witnesses seemed to be more effective at helping the defense in the respective trials in which they testified, and what made he/she more effective?

Books needed are 

Robert Traver, Anatomy of a MurderISBN 978-0312033569

Agatha Christie, Witness for the Prosecution