Othello as the tragic hero in Othello reveals one of Shakespeare's often used dramatic techniques - (Othello's) dramatic character. The audience is aware that it is now too late for the "honorable murderer"(V.ii.298)( a contradiction in itself) and is persuaded that, despite his shortcomings; being "one that lov'd not wisely but to well;" Othello's character is developed to its full potential. The fact that he fell victim to Iago's manipulating makes him all the more unfortunate and deserving of the audience's sympathies.
Building on Othello's character, he is, in this speech, calm and accepting, even humble; the characteristics of an honorable military man who has "done the state some service." His speech becomes almost a summary of events as he has fallen from grace through these "unlucky deeds" and is attempting to show his remorse as he "drops tears." The momentum builds towards the end and prepares the audience for the only possible conclusion.
Othello distances himself from the character that has killed Desdemona by talking of himself in the third person, again adding to the dramatic effect and the fact that Othello has acted out of character and "traduc'd the state" being nothing more than a "turban'd Turk." Metaphorically, Othello will rid the Venetians of "the circumcised dog" as he "smote him - thus" stabbing himself to complete the picture of this outsider with whom Othello can no longer even associate himself with.
The irony contained in Othello's final speech when, having been "perplexed in the extreme," he is inclined to murder "a pearl richer than all his tribe" due to jealousy and yet claiming that he is "not easily jealous," reinforces the dramatic irony that the audience has become aware of as it has watched Othello fall victim to "honest, honest Iago," the audience being well-aware that Iago is "a very villain else" (IV.i.126).