When Mac is watching video of the fight, it obviously isn't from fixed web-cams. The views, zooms and angles could only have been filmed by a live cameraman in the middle of the action.
In the opening scene when the two construction workers are fighting one is being held down while the other one threatens him with a jackhammer. The one construction worked slams the jackhammer into the cement to the right of the other mans head & when he starts using it blood spurts out. When the man being held down is released and rolls away the blood is on the left side of his face, which would have been facing away from where the blood is coming from.
When Sheldon is checking the blood to see if it is human in the beginning, we see only one red line present. With this type of tester, one line means that the control is positive, indicating that the test is working correctly, and that the test is negative. With two lines, the control is positive, and the test for human blood is also positive.
Whale bone is unlikely to have been common on viking helmets, as vikings didn't wear horned helmets. The horns are an American addition.