Enter Castle Neverwinter at #11 in the Blacklake District and proceed to the throne room. If you have Avral’s Journal from the Bryce Crypt you’ll be able to give it to Lord Nasher for 500xp and 200gp.
Speak to Sir Nevalle to commence the trial. It is possible to pull off a trial victory here. It helps to have done the following:
Whether or not you win the trial is immaterial. What you do, succeeding at skill checks or character influences and so on, only affects the specifics of the cinema. Everything comes down to the same event, an appeal by Trial of Combat. If you lose the trial, Sand invokes the appeal. If you win the trial, Torio Claven invokes it.
You are up against Lorne, the bald headed brute you’ve seen in several cutscenes. But first you must go to the Temple of Tyr in order to undergo the Rite of Tyr. You’re supposed to be alone, but that doesn’t stop some of your companions from interrupting.
At least two of them offer to join, while another can offer some insights into beating Lorne. At the outset, it must be noted that Lorne is a brutally tough melee fighter. Once you bring him to near death, he’ll go into frenzy mode. What this means is that he’ll be invulnerable and able to deal out truly hideous damage. So anyway …
Khelgar offers to fight in your place first. You can oblige, with the option of then choosing somebody else later. I wouldn’t recommend this unless you have higher influence with Sand than with Qara. The reason is that if you’re on better terms with Sand, he’ll offer two potions, one of which is a Potion of Invisibility to tip matters into your favour. The idea then is simple. Have Khelgar bring Lorne down to near death. Once Lorne hits frenzy mode, Khelgar can then drink the Potion of Invisibility. This makes running away from Lorne during his frenzy mode much easier. Once enough time elapses (about a couple of minutes) Khelgar can then simply walk in and deliver the coup-de-grace.
After Khelgar leaves, Qara offers to fight in your place. You can accept this without offending Khelgar apparently. This is quite easy if you have the right spell selection for Qara. The following sequence works handily:
There are other possibilities as well. If your PC is male, and if you have higher influence with Neeshka than with Elanee she'll offer to sabotage Lorne's equipment. As far as I can tell, this has no noticeable effect on Lorne's ability to waste his opponent. If you have higher influence with Elanee, she simply has some sentimental words to share with you.
If you PC is female, either Bishop or Casavir will offer to fight in your place, depending on whom you have higher influence with. If you decline Casavir's offer, he'll still give you a healing potion to aid you.
Hopefully this provides you with some insight if you decide your own PC is to do it. If your own PC decides to handle the fight, Grobnar can sing a song to confer a combat bonus if you influence with him is high enough. Lorne will be defeated but not fatally injured. He’ll throw out some parting words in an attempt to save face. If you had one of your companions do it for you, he’ll simply die upon defeat.
Once it's over, you’ll be treated to another cinema where Black Garius fumes at Torio over how matters turned out. If your PC handled Lorne instead of one of your companions, Garius will now kill Lorne having decided that Lorne has outlived his usefulness. In the meantime, you’ll find yourself back in the Sunken Flagon. You’ll find a chest that holds Lorne’s Falchion and a Belt of Hill Giant Strength. If you successfully persuaded Lord Nasher to enter a not guilty verdict, you’ll find another chest that holds the Amulet of Truth.
There’s now a few odds and ends you can tie up. West Harbor is now available again on the World Map. You can now bring the unhappy news about Lorne to Retta Starling for 500xp.
If you now make a trip to Port Llast, you’ll get ambushed by a rival adventuring party that wants to collect a Luskan bounty on your head. They’ll include the classically clichéd group of four, a Fighter, a Rogue, a Wizard and a Cleric. Among their corpses you can now loot a Half Plate +2, Bracers of Dexterity +4, a Short Sword of Quickness, a Ring of Divine Power (2), a Long Sword +2, Scarab of Protection +2, Elven Chainmail, a Drow Piwafi Cloak and a Major Circlet of Blasting.