Another counter example to the rules.
We were in Oaxaca on a road called Ferrocarril I think (means railroad) - used to be train tracks but now a pedestrian walkway and/or bikeway in a wide island down the middle. There are three lanes of traffic in each direction - traffic lights and topes of course.
We learned the hard way that in many places the left lane is for left turns and there is a traffic light arrow to indicate left turns. In some cases the left arrow comes on before the green light for the other lanes and in other cases the green arrow comes on after the green light for the other lanes.
Of course the right lane is clogged with buses.
So if you get in the left lane but still want to go straight you are going to make some left turn vehicles unhappy when you don't move because you are waiting for the straight ahead green light - or in the other case the left turners are waiting for the green arrow to turn but the straight green light says go - you can't move in or out of the left lane.
So lesson learned - at least on this one particular road the rule is stay in the middle until you know you want to go left or do a retorno.
Everywhere we go we find different situations - just as we do in the US. But the point of the above post is that there is an actual law in Mexico about left turn procedures.
Yes we do know who the victims are but it would be up to them to post if they so desire. Their story to tell - I am just relaying info about the law as it was explained.