Final answer:
The officer's comment 'it's probably right under our noses' is verbal irony because it implies the murder weapon is near yet undiscovered, which is opposite to what is actually meant if the weapon is indeed close by.
Step-by-step explanation:
The phrase 'it's probably right under our noses' signifies verbal irony because it suggests that the murder weapon they are looking for is in close proximity, perhaps even in plain sight, yet undiscovered. Verbal irony is a figure of speech in which what is said is the opposite of what is meant.
This statement is ironic if the weapon is, indeed, near the officers and they remain oblivious to its presence, highlighting a contrast between the officers' expectations and the reality of the situation.