util.effect on hitgroup?

[kpjVideo]

Hello, I'm trying to create a spark effect on a player when he is headshot. (TTT Gamemode)
After digging through the player.lua file I found this function but I can't seem to get this to work:

function GM:ScalePlayerDamage(ply, hitgroup, dmginfo)

   if dmginfo:IsBulletDamage() and ply:HasEquipmentItem(EQUIP_ARMOR) then
      -- Body armor nets you a damage reduction.
      dmginfo:ScaleDamage(0.7)
   end

   ply.was_headshot = false
   -- actual damage scaling
   if hitgroup == HITGROUP_HEAD then
        -- EFFECT SHIT STARTS HERE
         local effectdata = EffectData()
            effectdata:SetOrigin( ply:GetPos() )
            effectdata:SetNormal( ply:GetPos() )
            effectdata:SetMagnitude( 8 )
            effectdata:SetScale( 1 )
            effectdata:SetRadius( 16 )
         util.Effect( "Sparks", effectdata )
      -- headshot if it was dealt by a bullet
      ply.was_headshot = dmginfo:IsBulletDamage()
      local wep = util.WeaponFromDamage(dmginfo)

      if IsValid(wep) then
         local s = wep:GetHeadshotMultiplier(ply, dmginfo) or 2
         dmginfo:ScaleDamage(s)
      end
   elseif (hitgroup == HITGROUP_LEFTARM or
           hitgroup == HITGROUP_RIGHTARM or
           hitgroup == HITGROUP_LEFTLEG or
           hitgroup == HITGROUP_RIGHTLEG or
           hitgroup == HITGROUP_GEAR ) then

      dmginfo:ScaleDamage(0.55)
   end

   -- Keep ignite-burn damage etc on old levels
   if (dmginfo:IsDamageType(DMG_DIRECT) or
       dmginfo:IsExplosionDamage() or
       dmginfo:IsDamageType(DMG_FALL) or
       dmginfo:IsDamageType(DMG_PHYSGUN)) then
      dmginfo:ScaleDamage(2)
   end
end

Would anyone happen to know what I'm doing wrong?
Thanks

[Rubat]

util.Effect( "Sparks", effectdata,true,true )