This is the version in "Naomi Wise: Creation, Re-Creation, and Continuity in an American Ballad Tradition" by Eleanor Long-Wilgus (from what she says is an 18th century broadside in the Harvard College Library):

Young men and old, I now make bold,
Pray lend to me an ear,
This is as cruel a murder,
As ever you did hear.

All on a lovely female
Her age was scarce 16,
Her beauty bright did me delight
Our hearts she did ensnare.

Her rosy cheeks and milk-white skin,
The fairest of the fair,
Because she had no fortune
I did the maid betray.

This creature being an orphan,
As you may see,
So when I got my will of her
I proved her destiny.

This girl was a servant maid
And I a farmer's son,
All in the County Longford,
Convenient to Rahone.

In private there we courted
till I got her with child.
And then to take her precious life
I planned it in my mind.

'Twas on a Sunday evening,
as quickly you'll hear
I Sent for her in private
and soon she came to me.

I said, dear Anne if you comply
To Longford we will go.
And both there get married.
I am sure no one will know.

"Twas late that night we went across the country,
It would draw tears from your eyes
When I was going to murder her, I made her this reply.
"Now, Anne, youl'll go no further,
for here you are to die."

"Oh, James, think on your infant dear,
and don't give me a fright.
Nor don't commit a murder
this dark and dismal night.

"I'll promise God on my knees,
if you spare my life,
That I'll never come to trouble you
or seek to be your wife."

What she said was all in vain,
I gave her dreadful blows,
With a heavy loaded whip
I left her in her gore.

Her blood and brains fell like the rain,
Her moans pierce your heart;
I was sure that I had murdered her
Before I did her part.

She was alive next morning
just by the break of day,
There was a shepherd's daughter
by chance came that way,

She seen her lying in her blood
And came to her relief,
Saying, I was murdered here last night.
Will you bring me to a priest.

The priest and the doctor was sent for,
and the policeman likewise,
When they got information
They went in disguise,

Its quickly they surrounded me
For she told my name.
They brought me back a prisoner,
and lodged me in Longford jail.

I lay there with a troubled mind
Until my trial day,
The jury found me guilty,
And the judge to me did say,

Now, for this cruel murder,
On an orphan, all may see
On the 29th of April
You die on the gallows tree.

My name is James M'Donald
My life I now must part.
For the murder of Anne O'Brien
I am sorry to the heart.
But I hope the Lord will pardon me
Against the judgement day.

(Text as it appears in her book).

Malcolm, I agree that 19th century seems more likely than 18th, because of the reference to "policeman", but who am I to dispute my mother?