A lawyer in court yesterday made reference to "an incident" Tuesday night -- this is the incident. Sources involved in the situation tell TMZ ... people in the house were "alarmed and nervous" after hearing Katherine sounding heavily drugged.

In addition to attempting to 86 the security team, Katherine ordered Trent Jackson off the property. You may recall, Jackson's security -- and Trent in particular -- thwarted Monday's attempt by Randy, Jermaine and Janet to take the kids to Arizona.

Our sources say the prevailing view is that Randy and company have drugged their mom.

We're also told Jackie Jackson is furious at his conspiratorial siblings for what they've done and what they are trying to do.

We were unable to get Randy for comment.