Having already won the first trick, with 3 trump still in his hand the maker should now lead trump.
BTW S1's lead is incorrect. Gotta lead that AS in that spot especially with L+1. There's a number of reasons why:
1) by leading your off ace, you give your P an opportunity to short-suit themselves.
2) Think about what your P wants you to lead if they have a hand with euchre potential. When that's the case your P is praying you lead an Ace so they don't get squeezed off a trump. This ace lead allows your P to safely throw off and make his hand even stronger.
3) An Ace lead forces the enemy to burn a trump on the first lead. This is important. Your ace getting trumped isn't all bad. By forcing the enemy to spend a trump on the first lead their probability of getting a 2 pt march drops significantly. Conversely, when you lead a garbage card and the enemy wins that trick without spending a trump, their chances of getting a 2 pt march just went up.
4) When you lead a doubleton or tripleton ace and you catch the dealer/maker with the same suit, you can then double lead that suit those times you think the maker has another one and get a cheap trick for you P when they trump in. This ploy leads to ALOT of euchres especially when S1 has the Right or L+1 like in this hand. With S1's specific holding not leading his AS is actually a large mistake.
Becuz of 2) and 4) it's a safe bet that vs dealer calls leading off aces maximizes euchre potential for the defending team. And to me that's what defense is all about:
Always play for the euchre. It will usually be the case that there is no way to prove mathematically which line is best on defense. The best rule of thumb we will ever have in those spots is to take the line that maximizes euchres.
IMO, this is one of the great leaks I see every Monday/Friday night games. Too many times S1 has an off ace and leads garbage instead, making it that much harder for their team to ever get a euchre.
What lead is best vs a 2 seat call is more complicated, but vs a dealer call, I'm always leading an ace becuz I wanna maximize my team's chance at a euchre.
I'm even leading a quadrupleton Ace as it will still likely force out enemy trump. There is some debate about leading tripleton or quadrupleton aces. The debate goes, don't lead those aces. Save them til the end after trump has been led and they may now win a trick. There is certainly truth to that, but that's just one side of the coin. There's still little to no evidence indicating that saving those aces til the end is actually better than just leading them. Since the evidence is unclear, might as well lead it and capture all the above positives from doing that, including maximizing euchres.
BTW if S1 always leads Aces vs dealer calls (excluding those times S1 should lead trump instead), this also gives his P information he can utilize. If S1 doesn't lead an Ace, his P will know he has none, and that can change the way he plays his hand those times he has a hand with euchre potential.