Well, an accelerated stall certainly appears to be the final slice of the "swiss cheese" of sorts.
I'm not an accident investigator but:
1. Appears to be a little 'get home itis"
2. Circle to land approaches are challenging
3. Didn't have a plan on how to execute the circling procedure.
4. Got "lost"
5. Got slow
6. Got low
7. If the pilot saw the runway at all, he didn't handle the turn from base to final well and (I think) had an accelerated stall (whenever you bank, your stall speed increases as you load the aircraft) and didn't have altitude to recover.
I've got "CIRCLING APPROACH, VMC ONLY" on all my jet types for a reason.
1. Get-home-itis with a whole lot more of normalization of deviance sprinkled in. They cancelled IFR so they could shoot this maneuver to get in and had done so many times before. The approach plate forbid circling at night. Which is why they canceled as soon as they picked up the field initially.
2. True. Especially when it's night, in terrain, in borderline weather. My personal limits are to pick one of those. If its night, no weather, no terrain. Or terrain, no weather and not at night.
3. They had done it many times, which probably made them complacent. I'm sure the plan was there, just wasn't executed properly.
4. Yup
5. Yup
6. Yup.
7. I'm certain it was lost in the city lights. He calls the Tower and asks to turn up the lights as they are making their way around. Tower says they are all the way up just before the yelling begins.
8. I am with you Derg. Accelerated stall. Turning left. Head is probably left looking over his shoulder trying to find the field, and either picks it up and tries to pull the airplane around to the field or realizes he's low and is staring at a piece of dirt ahead of him and pulls back either to climb or increase rate of turn. Either way the resulting accelerated stall was the final broken link.
I have never flown a Lear 35 but if it is like all the other small business jets I have flown you aren't on the rudders too much when both engines are running. Less likely cross control, and more likely accelerated.
Good view of the ground track.