J. A. Scott's "oral tradition" text does not appear in the original edition of Frank Moore's book, published in 1860.

The broadside titled "Polly Wand" was apparently published around 1810, not 1777. (It was purchased by a collector in 1813; I've found no evidence for an earlier date.) You can view the broadsheet, titled "Polly Wand, together with The Beggar Girl and Tom Stoppard," at the American Antiquarian Society's website. It differs considerably from Scott's version:

Come all you brave shooters that follow the gun,
Beware of your shooting by the setting of the sun,
It was a doleful thing that happened of late,
It was Polly Wand whose fortune was great.

As Polly was a walking by the setting of the sun,
She stepped under a green branch the shower to shun;
As her true love was hunting he shot in the dark,
Alas, and alas! Polly Wand was his mark.

And when he came to her and found that it was she,
His joints they grew weak & his eyes could scarce see,
In his arms he embrac'd her till he found she was dead,
And a fountain tears for his own true love he shed.

Then he ran home with his gun in his hand,
Saying daddy, dearest daddy, I have shot Polly Wand;
I shot the fair female the bloom of my life,
For I always intended to make her my wife.

In two or three days after Polly Wand did appear.
Crying Jemmy, dearest Jemmy, you have nothing to fear
Stay in your country till your trial comes on,
You shall not be condemned by the laws of the land.

In the height of his trial Polly Wand did appear,
Crying uncle, dear uncle Jemmy Rander must be clear,
For I'd my apron about me when he shot me for a swan,
Alas, and alas! it was I Polly Wand.

There were fourteen of them all sitting in a row,
Polly Wand in the middle like a mountain of snow,
I'd my apron about me when he shot me for a swan,
It's a woe and alas! it was I Polly Wand.

The "fourteen in a row" may be the jury. Or, if you're so inclined, you may interpret them as angels accompanying Polly.

Either way it's a great line.