Sort of impossible to time an engine with a timing light if it won't run. And trying to see if its timed while turning the ignition key is not going to give any sort of correct timing mark.
Sure, it may flash whenever it passes #1 cylinder, but the engine is advanced by the ecu when starting, and can bounce all over the place while cranking, so you'll never get close enough to see if its off. And I doubt you'll be able to spin the engine fast enough to really see the timing mark work to your favor.
The only way to see if the cams have slipped is to manually set them. One way to see if they are out of time is to set crank at TDC, pull #1 plug, check piston for TDC (making sure its not 180º out, if it isn't, spin engine another 360º and re-check piston for TDC), then use a leakdown tester to see if it holds pressure. That will tell you if the valves are completely closed, which will tell you whether the cam slipped or not. If you hear air leaking through and cannot get pressure to build to at least 75psi (while set at 100psi for test), turn the crank slightly back and forth while watching the gauge. Where it shows the highest pressure, look at the crank, that's how far off the cam is.
Furthermore, you can have one side out and not the other, depending on what tooth slipped, so you'll now have to a cylinder on the other side (spinning the motor 360º first), although I can't remember which one is closed when at TDC. I think its #5, but don't quote me on that.
This shouldn't take much more than about 10-20 minutes to check, and will tell you right away if the cams are not in the right position.
Of course, if you don't mind pulling the front cover, that would be the best way to check if the marks are lining up.
