To analyze this situation, try approaching it like a protest committee would. That is, start out by writing out all the facts of the incident. This is actually the hardest part of being on PC. A lot of protests hinge on exactly what facts are found. Also, different people will see the exact same event in very different ways - often giving completely different (and still completely honest) accounts.

Here's how I see this incident based solely on the video.


Facts:

Time 0: The very first frame shows boats rounding a leeward mark, leaving it to port. The video then switches to boats rounding a mark to starboard. This leads me to conclude that this incident happened at a leeward gate.

Time 1: At that point, it shows 4 boats - One going upwind on starboard tack (SU1), one going upwind on port tack (PU), one going downwind on starboard tack flying a red spinnnaker (SD/red), and one going downwind on port tack flying a black spinnaker (PD/black). Based on where I conjecture the mark to be, SD/red and PD/Black are outside the zone. PU is behind SU. PD/black and SD/red are overlapped and to windward of PU and SU. The boats converge and their relationships hold until 0:02 in the video.

Time 2: At 0:02, another boat, sailing upwind on starboard tack (SU2) to leeward of the others, enters the frame at the bottom. PD/black also turns downwind slightly.

Time 3: At 0:03, SU1 sails away from the other boats, towards the top of the frame. SD/red, now approximately 1 boatlength from PD/black, starts to turn downwind. PD/black holds course. PU bears away about 1/2 second after SD/red changes course.

Time 4: At 0:04, SD/red's boom changes sides. She is now on port tack, to windward of all the other boats. SD/red is on the edge of the zone. PD/black is outside the zone. The two are still overlapped.

Time 5: About 1/2 second later, SU2, sails past PU to leeward. PD/black lets her spinnaker flog. SD/red's spinnaker pole contacts the skipper of PU. The force of contact spins SD/red around ahead of and slightly to windward of PD/black. It is unknown if there is any damage or injury.

Time 6: At 0:05, SD/red and PU disconnect. PU rounds up and sails across SD/red's bow. PD/black douses her spinnaker, bears away slightly, and gains an overlap to leeward of SD/red. SD/red is two hull lengths from the mark. PD/black is three lengths away.

Time 7: The boats involved sail away from each other. PD/black rounds the mark inside of SD/red. SD/red sails past the mark while dousing and rounds after PD/black and one other boat.


Conclusions:

Time 1: SD/red must keep clear of SU under rule 11. PU must keep clear of SU and SD/red under rule 10. PD/black must keep clear of PU under rule 11 as well as SU and SD/red under rule 10. At this time, all boats do.

Time 2: PD/black's course change is inconsequential. SU2 must keep clear of SU1 under rule 12. The other boats must keep clear of SU2 under rules 10 or 11.

Time 3: Because PU and SU2 are leaving the mark, Rule 18 does not apply between them and SD/red and PD/black (see rule 18.1(c)). Rule 18.2(b) does not yet apply between SD/red and PD/black because the boats are outsize the zone (see rule 18.1). Rule 18.4 does not apply because SD/red is not the inside boat. The relationship between PD/black and SD/red is governed simply by rule 10 - and PD/black is required to keep clear of SD/red. SD/red takes avoiding action (bearing away and then gybing). Therefore PD/black breaks rule 10.

Time 4: SD/red is now on port tack to windward of PD/black. SD/red must keep clear of PD/black and PU under rule 11. Because PD/black and PU gained right-of-way as a result of SD/red's action, they are not required to give SD/red room to keep clear under rule 15. SD/red must give PD/black mark-room under rule 18.2(b).

Time 5: SD/red does not keep clear of PU. SD/red breaks rules 11 and 14. Because it was not reasonably possible for PU to avoid contact (she bore away as SD/red was changing course), PU does not break rule 14.

Time 6-7: SD/red gives PD/black mark-room. No further rules are broken. SU1 and SU2 never took avoiding action.


Decision:

Assuming no on-the-water penalties were taken, PD/black is disqualified for breaking rule 10. Because SD/red was compelled to break rules 11 and 14 as a result of PD/black's illegal action, SD/red is exonerated under rule 64.1(c).

I hope that helps,
Eric