Two or three eyewitnesses are required before the Elders can take action against a baptized Jehovah's Witness. Deut. 19:15; John 8:17
If someone sees you breaking rules, no big deal. Two or three eyewitnesses are required. Hearsay and gossip is not good enough.
If only one person saw you, then it's just their word against yours. According to the 2010 Elder's Manual, Shepherd the Flock of God, p. 71, nothing can be done if there's only one eyewitness. No action can be taken by the Elders against you.
Of course, there are special circumstances and various scenarios, that may raise suspicion that you're up to no good. e.g. let's say two or three different eyewitnesses see you breaking the same rule, but on separate occasions. In such a situation, the Elders can consider the testimony of eyewitness in order to prove your guilt.
It's hard to defend yourself at judicial committee meetings if you don't know all the rules and all the loopholes. Find a copy of the 2010 secret document for Elders only. It's called Shepherd the Flock of God. You'll learn what the rules of the organization are and how the Elders are instructed to enforce those rules.