Before the speech, I cast an [color=blue]Aura of Ennobled Presence on myself.
I also spont a spell (based on the same guideline as [color=blue]Notes of a Delightful Sound) to help my voice to be "clearer, sharper, and more distinct", and thus, better heard.
Something like this
Base 1, personnal, +2 sun, final level 3.
I ritual spont this without fatigue before the speech (sun duration 
), casting total (14 + aura 3)/5 = slightly more than 3.
Bold entries are said with a booming voice.
I trust the crowd includes both the covenfolks and the villagers?
[color=red]Welcome to you all.
As some of you may know, my name is Ardath, and I am one of your new lords.
We gathered you today to witness our judgment of this woman (points to the girl).
[color=red]As she confessed, she killed her husband while the man raped her, thus depriving us of one of our servants.
We do not take neither of these facts lightly, and deliberated a long time on what we should do.
We talked to the girl, and she confessed her crime, asking no penance for her deed.
This, then, is our judgment!
This, then, is our justice, towards anyone who would harm us, or one of your servants!
There, Mariella (if she agrees, as this would give the best impact. If not, a covenfolk will do the job) casts her almighty Ball of Abysmall Flame on the (false) girl and her stake. The impressive conflagration instantly reduces it to a burning inferno.
I wait a little for the awed and probably very frightened crowd to calm itself, and then, with a booming voice...
[color=red]But this is not all I had to tell you!!!
Resuming a more normal voice...
[color=red]We judged this woman for her crime, and she paid for it. But know that we consider what her husband did to be as much of a crime!!!
I told you that we won't let anyone harm one of you, and, by this, I meant everyone, even another of our servants. And this include the man, any man, who would rape a woman.
Had this poor margarete came to us for help instead of killing this guy, we would have judged him today, not her.
I don't want to see this kind of thing happen again. Never. I trust any violent man among you will understand the message.
But this is just one point.
As of now, know that your old life is over, and that a new, better life, begins.
We intend man and women to be equal in rights before the law, even if they may have different duties. And we intend the law to be fair and just.
We intend to give you the chance to improve your life, and the life of your family. We want to raise you all from poverty, and make of this village a striving and rich community. We've already begun this, through a latin school which will educate your children and make them learned scribes, and through a milicia, which will make your village a safer place, protect you from criminals and bring them to justice.
We plan to continue, by improving everything we can improve, and to bring forth crafstmen here.
We want to give you a chance to raise above your station, and use your natural gifts to their full extant.
Have you ever dreamed that you deserved better that this? Well, we're here to give you your chance!
Those who serve us faithfully and who demonstrate skill will raise to join the ranks of the covenfolks and, maybe, one day, become a trusted custos. No talent will be wasted, not if we can avoid it.
More than all perhaps, we want to make you all willing partners to this.
The milicia will rise and grow from your ranks as the village will grow.
The future scholars will be your children.
We want you to appoint a representative before us, who will relay to us your problems, and explain to you our wishes and decisions. Yes, incredible as it may sound, we actually care about our welfare 
As per the law, we will judge the more serious crimes, but a tribunal will judge the lessers. We will appoint half of the judges from the ranks of the covenfolks, but the villagers will choose the other half from their ranks.
And this is just the beginning. Sure, there will be tough times, and difficulties, but, together, we will prevail, and make this place a better place to be.
(points to a an undefined place in the crowd, so that people wonder if she's talking to them while feeling more personnally questionned)
[color=red]Tell me, do you trust me?
(Quickly points to another place before anyone as taken up the speech)
[color=red]And you, do you? Well, if you don't, you're wrong. What about an exemple?
Some of you have expressed the desire for a church. Some of us don't share your faith. But, still, we all agreed to help you build it, as a proof that, while we want our authority to be undisputed, our will to be absolute, we will respect you and your wishes, listen to you, and treat you as best as we can. And we will build you the best church you've ever seen here. (OOC: Ok, this is an easy promise, but hey, this is politics, right? )
[color=red]In time, we'll make you know more of our decisions. But trust me on this: If you serve us loyally and faithfully, to the best of your abilities, we will reward you, protect you from harm, and make your, and our, wildest dreams come true.