To make execution and decapitation fit the rules better, there are:
If “triple damage” is possible on a lucky shot, then in a set-up situation where luck doesn’t come into it, it ought to be possible as well. So a strong man (but not a musclebound thug) with ST 11 starts at swing 1d+1, adds +1 for a sword, adds +1 for a fine blade, and adds +2 more for All-Out Attack (Strong). His damage roll is 1d+5, or 6-11. To the neck, that’s 12-22. Triple it for ideal circumstances with all the time in the world, nobody fighting back, and endless practice — let’s say that a Professional Skill (Executioner) roll allows this — for 36-66. Average is 51. That’s -4xHP for most people, -3xHP for some really big ones. Three or four HT rolls are needed to survive. If the guy doesn’t die (low damage, high HT), the rare second blow will mean an average of 102, which is automatically lethal even at 17 HP.
Those who want to postulate monstrous guys with 20 HP and HT 18 will be introduced to my bigger executioner with ST 13 and a very fine blade, who will do 2d+4 and average 66 points a chop.
My suggestion: Steal from the Forced Entry skill as well.
Professional Skill (Execution): IQ/A
This is the knowledge of how to kill another person quickly and cleanly in a controlled situation. It is of no use if you do not have complete control of your target and access to appropriate equipment (i.e., an executioner’s sword as opposed to a normal combat-oriented sword, a chopping block, etc.) Add +1 per die to the damage done to the subject if you know this skill at IQ+1, or +2 per die if you know it at IQ+2 or better. Decapitation takes at least five minutes to set up (use standard rules for reducing or taking more time) and requires a roll against this skill as well as an attack roll against the subject’s neck (almost always an All-Out Attack after Evaluating, net modifier +2). If both rolls are successful, the damage is tripled (for a net x6)!
That’s fairly generous, but frankly, for executions that don’t involve supernatural targets, I’d usually just call it death by fiat anyways. Brings the range of damage from 36-66 up to 48-78 for a skilled executioner, the average of which is enough to easily auto-kill a HT 10 man. A poor damage roll or higher HT target allows for survival rolls, which might necessitate another chop.
Another suggestion is to add decapitation to the to the dismemberment rules. A limb requires HP injury, so it follows that the neck might require HP×4 injury (or HP×2 penetrating damage), which would require 20 damage for the average human. Then, I thought about the spine hit location in GURPS Martial Arts. Of course, this has been asked before, and Kromm said:
Cervical Vertebrae (-11): Crushing, cutting, impaling, piercing, and tight-beam burning attacks from behind can target the spine in the neck. The vertebrae provide an additional DR 3. Use the wounding modifiers for the neck, but any hit for enough injury to inflict a shock penalty requires a knockdown roll, at -5 if a major wound. Injury in excess of HP cripples the spine. This causes automatic knockdown and stunning, plus all the effects of Quadriplegic (p. B150). Roll after the fight to avoid gaining this disadvantage on a lasting or permanent basis! A miss by 1 hits the neck.
So, this is getting crazy! I’ll say that decapitation can only come from targeting the cervical vertebrae (which only makes me think of my fun time with cervical radiculopathy). That -11 penalty will be hard to soak along with that DR 3. I’d be willing to say then, at that point, HP×2 injury is enough to decapitate, which is going to require 13 damage.
A true longsword (i.e., the GURPS bastard sword—they’re essentially flipped in name) wielded in one hand by a ST 10 individual can do a maximum of 7 damage, or, wielded in two hands, can do a maximum of 8 damage. A greatsword wielded by a ST 12 individual can do a maximum of 11 damage or 12 damage if it’s a falchion (rule from GURPS Low-Tech Companion 2: Weapons and Warriors). An All-Out Attack (Strong) can gives +2 damage to each of these examples, which lets the greatsword do it regularly, and, honestly, that doesn’t feel right.
By the time I had finished writing that paragraph, I started considering HP×3 injury, which would require 18 damage, and that number is much closer to the original 20 damage. It’s -2 to damage but also -6 to skill. So, I think the 20 damage to the neck (-5) works cinematically and that 18 damage to the cervical vertebrae (-11) is probably a bit more realistic. One would need ST 16 and a falchion greatsword doing an All-Out Attack (Strong) to even have a change of doing this in combat—that’s 2d+6 damage for maximum of 18 damage. Maybe Hafþór can try. Of course, if the ST 16 individual has Weapon Master and the falchion greatsword is very fine, that raises it to 2d+10 damage for an average of 17 damage, which is just shy of the 18 damage required.
Where does Professional Skill (Execution) fit into all of this? Well, let’s say that the more realistic executioner is that ST 12 individual wielding a falchion greatsword for a minimum of 7 damage, an average of 9.5 damage, and a maximum of 12 damage. Being able to triple minimum damage to 21 ensures a clean cut every time. I’d probably base it off of Power Blow a bit more, so one can either get ×2 damage or ×3 damage, depending on skill and time, which may allow for some combat use.
Anyway, thinking about damage/wounding multipliers got me in a tizzy! Multipliers don’t make much sense for logarithmic damage (which might be important if I’m using Knowing Your Own Strength, though I’m still not sure if KYOS damage is “logarithmic” or not). But changing cutting to +2 injury and impaling to +3 injury doesn’t scale either—because HP are still quadratic. Well, scaling back HP actually makes it worse in some cases unless I used some kind of system for logarithmic injury—e.g., 7 injury plus 7 injury isn’t 14 injury, it’s 10 injury (because doubling the value is a +3 under logarithmic ST). But do you have to do 10 more injury to get to 13 injury or is another 7 injury wound enough? How far down does the rabbit hole go?
And I never figured it out for sure. Of course, this will work with standard damage. It gets messy with Knowing Your Own Strength. And throw Conditional Injury in there? Then, it’s back to the drawing board.
But, if you want it to work with CI or both KYOS and CI, then I’d say that decapitation requires a Severity 3 wound, which feels like a nice little bonus for a huge -11 to hit. Normally, it takes Severity 4 for an instantly fatal wound, but Severity 3 can do it if you’re cutting at the cervical vertebrae. Sounds fair enough to me! If you can do 6 more damage to the neck, though, you’re better off not trying to soak up an additional -6 to hit.