A couple have been awarded compensation of $3.25m (£2.53m) after their adopted baby son was murdered by his birth father, weeks after he regained custody of the child.

Rachel and Heidi McFarland sued their lawyer Jason Rieper for malpractice after he wrongly led them to believe three-month-old Gabriel's biological parents had signed release-of-custody papers.

The couple had arranged to adopt the child from Rachel's teenage co-worker Markeya Atkins and were present at his birth in Des Moines, Iowa, in December 2013.

But Ms Atkins later changed her mind and reclaimed custody of the child, which she was able to do because she had not signed the release forms.

Five weeks later the infant was shaken to death by his 17-year-old father, Drew James Weehler-Smith. The teenager was later convicted of second-degree murder and jailed for 50 years.

Rachel and Heidi McFarland adopted Gabriel at birth but were forced to give him up: KCCI

A judge at the Iowa District Court for Polk County awarded the settlement after ruling the lawyer acted negligently.

"The release-of-custody never got signed by either birth parent. Obviously our child and us weren’t a priority to [Mr Rieper]," Rachel told People magazine. She added she did not expect to receive much of the compensation.

"We are just happy he was found negligent," she said. "That was what our goal was. We will not see any money from this."

After coaching his biological mother through labour, the couple had Gabriel for 78 days after his birth.

Rachel said: "Adoption wasn’t ever our number one choice, but because it was private it seemed tailor-made for us and we thought this could be our chance to become parents.

Drew James Weehler-Smith admitted murdering his baby son (WHO-TV)

"The birth mum didn’t care if we were a same-sex couple. It just seemed too good to be true - and it was too good to be true."

They were told in March 2014 that Ms Atkins wanted her son back.

Rachel, who has since adopted two daughters with Heidi, said Mr Rieper said was nothing they could do about it.

"She wants him back and you have to give him back. It was horrible. There are no words," she added.

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Mr Rieper's lawyer said he would look to challenge the jury's verdict in the civil trial, which focused on the adoption case and not the child's murder.

"You can’t control the emotion of a birth mum, and you can’t control the emotions of a 16 year-old birth mum,” said David Brown. "At the end, the kid wasn’t going to [sign the papers] and the suggestion that Jason was to force her to do it, would be unethical for him."

But Roxanne Conlin, who represented the adoptive parentst, claimed Mr Rieper "just didn't get around to" getting the forms signed.

"If the lawyer had done what he was supposed to do, the birth mother would have signed a document called a release of custody and four days after she signed it, it would have been almost impossible for her or the baby's father to take Gabriel away from them," she wrote on Facebook.