If the one guy did nothing but film on his own initiative, I suspect he probably isn't guilty of anything. But if he was part of an organized plan to detain the guy, then that may be enough for him to be guilty of conspiracy to detain Arbery unlawfully. But without having seen all the evidence and all the jury instructions, I wouldn't have a strong opinion either way.
I have seen cases in the news in which judges and lawyers argue for hours in an effort to determine if something is "unlawful" while the cop had to make a decision in a few hundreths of a second.
The law uses something called "the reasonable man" standard. Would a reasonable man chase after someone whom a neighbor alerted them to having bolted from a house which had been burglarized in the past? Would he do so if he was a retired cop?
Would a reasonable man, after having seen the video of this exact same guy going through the house (which had been burglarized) in the middle of the night four times, have reasonable grounds to believe this guy may have committed the previous theft, and may have just committed another one?
Would a reasonable man, knowing that a gun had been stolen recently from them, believe this man might be armed, and therefore necessitating themselves being armed as well?
But without having seen all the evidence and all the jury instructions, I wouldn't have a strong opinion either way.
I have been told by others who claimed to have watched the trial that Arbery's past history of criminal behavior was not admitted as evidence. Presumably this means the videos of his shoplifting and confronting a cop were not shown, nor his record of taking a gun to school and threatening people with it.
Also his brother is a criminal too.
This is a political show trial. The administrators of the state want a conviction so they can appease the mob. I think they've worked to slant as much as they legally can to obtain that result.