Insider trade on Splunk acquisition?

I know this isn't what happened, but what if one day I'm waiting for the bus and I over hear a guy talking on their phone about an imminent acquisition?

1. Would that still fall under insider trading even if the information was accidentally heard, and even if I wasn't 100% sure of its accuracy?

2. If I had no clear connection to the company how would it be proven that I was trading on insider information? Surely it's not enough just to say the trade was statistically unlikely, or is it?

The SEC has recently been pursuing very expansive insider trading definitions, and they are occasionally losing, so it’s very hard to say.

But traditionally in the US insider trading is not about market fairness, it’s about not stealing from shareholders. So if you have no obligation to the company or it’s shareholders you aren’t an insider. The phrase is “breach of a fiduciary duty or other relationship of trust and confidence”.

But I'm pretty sure I read a case of a guy who traded on a future acquisition and was convicted on insider trading charges. He surreptitiously overheard it from his fiance, who worked for the company. Doesn't this guy not owe a company he doesn't work for a fiduciary duty....?

There's a sliding scale of accountability from "I did it", "My wife did it", "My fiance did it", "my significant other did it", "my neighbour did it" to "some person I don't know did it".

A fiance is still close enough that they are captured by lots of regulation, because collusion/cooperation between partners is so common.