Saying that he felt suspicious is a statement of one's state of mind.
What year did you get your law degree? Mine: 1984.
As far as I know, Geragos and his cohort Harris also have law degrees.
Perhaps you are ill-informed because you have not read the actual transcripts, or excerpts from them. I would suggest that you buy the relevant pages, highlight in yellow the parts where you think Geragos did not adequately safeguard his client's interests from testimony YOU think shouldn't be admitted, and send it to him with a note. You might also want to send a note to the judge, reminding him of his dereliction of duty.
A lay witness can testify that, to him, Scott acted suspiciously.
Contrary to popular belief, lay witnesses can sometimes testify as to their opinions--or, as you expressed it, to "conclusions" made by them. [You said they were "speculative" conclusions, but they weren't speculative, b/c the conclusions of the witnesses were reached after actually seeing and being there.)
While California has its own evidence code, the fact is that the rules of evidence for each state have more similarities than differences. Because of that, the following passage, which is NOT from California, but is from another state, is applicable:
"[C]ourts historically have recognized a number of subjects about which a lay witness is permitted routinely to offer an opinion because such opinions are a shorthand rendition of the facts upon which they are based."
Lest you think that the witnesses are usurping the jury's role as the sole 12 people who are to decide if Scott is guilty, let me point out that for a witness to say (in essence) that Scott acted suspiciously, is for him to give proof of a fact that, if true, TENDS towards the ultimate conclusion that Scott is guilty. Obviously, that ultimate conclusion is for the jury to reach/not reach. But whether he acted in a certain way is highly relevant, probative of facts which are material, and it is permissible for a lay witness to describe his/her experience of how Scott was acting.