It was a frigid day in February last year when Samantha Green, high on methamphetamine, took her 19-day-old son through a muddy slough in northern California, authorities said.

That's where the baby boy, Justice Rees, wearing only a onesie, died in the cold.

"She said she was kidnapped and, 'My baby's dead. My baby's dead. It froze last night,' "Ricardo Villasenor, a bystander who found Green bloodied and barefoot, testified in court, according to the Sacramento Bee.

Green, 24, is on trial in Yolo County for the murder of her son.

Early last year, Green and her fiancé, Frank Rees, from Woodland, Calif., were posting photos on Facebook, showing their newborn son swaddled in a hospital blanket.

Prosecutors say Rees was a drug dealer and Green had been using methamphetamine while she was pregnant, according to the Davis Enterprise. The baby's paternal grandmother, Patricia Rees, had said the child was born with meth in his system, but when his parents' drug tests came back clean, they were allowed to take him home, according to the Bee.

Just 19 days later, Justice would be dead — lying alone in a freezing marsh in nearby Knights Landing, where prosecutors say Green was furiously trying to find her baby's father, who she believed was there with another woman.

Her attorney said she was suffering from drug-induced psychosis — a condition characterized by delusions and hallucinations.

"She had no business out there in the first place," Deputy District Attorney Ryan Couzens said last year, according to the Bee. "She left him out there in the mud."

The case, which seems riddled with more questions than answers, made it to trial late last week.

On Feb. 23, 2015, Green's attorney, Tracie Olson, said Rees wanted to have sex with Green and, when she declined, he gave her liquid meth anally — and then again and again — until she agreed, according to the Daily Democrat.

"Samantha has said repeatedly that things got hazy and dreamlike after that last shot of methamphetamine," Olson said during trial last week, according to the newspaper.

The prosecutor said that the couple planned to have sex with another woman that day; then Green decided she no longer wanted to and the two began to fight. Green later texted him, "I'm on my way babe, I love you so much," and took Justice with her to find Rees and the woman near a marsh in Knights Landing — where Rees and the woman were having sex in his car, according to the Democrat.

"The evidence will show she is jealous and that she is angry," Couzens said, according to the newspaper. "People get upset about cheating, but she takes it particularly bad."

With the baby boy in her arms, authorities said, Green went to look for them.

"Eventually, it got dark and she sat by a tree and passed out. When she woke up, her baby was next to her cold, not breathing, and dead," Olson said, according to the Democrat, adding: "She said he had been through so much she didn't want to put that poor little body through anything else."

So she turned to her dead infant and reportedly told him: "I'll be back."

On Feb. 24, Villasenor, who was working in his yard in Knights Landing, heard Green's screams. He said in court he thought it was a child calling, "Help, help," according to the Enterprise.

"I yelled back, 'I will be right there,' " he said in court.

Villasenor said he got in his car and drove around the embankment, where he found Green, who claimed she had been kidnapped and sexually assaulted. He said he called 911 and then handed her the phone.

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"I don't know what happened. I'm badly hurt. I can't walk. I've got bruises all over my body," Green told the dispatcher, according to audio presented in court, the Bee reported.

"Where's the baby?" the operator asked Green.

"He died," Green said, sobbing. "It was so cold."

Again, the operator asked where the baby was.

"I don't know," Green cried out. "I have no idea."

The next morning, search-and-rescue crews found Justice's body in tall grass near the marsh. Authorities said he died of exposure to the cold.

In March 2015, Green was charged with involuntary manslaughter and abusing or endangering health of a child, according to the Yolo County District Attorney's Office. The charge was upgraded to second-degree murder.

A Facebook user under Rees's name posted a message, saying he could not imagine the pain Green was going through and that "I pray that she is able to find peace."

"A month ago today at this very time (around 10:35 a.m.) was the last time that I saw my precious baby boy Justice Talliesen R-lee Rees," the March 2015 post says. "He was snuggled in his car seat with his binkie and his super soft zebra blanket he was happy. I looked at him and made sure that his lil feets were covered and his bottle was next to him (to keep it warm). I said bye bubbers I love you and kissed his lil forehead and while doing so felt his ears to make sure they we not to cold. That is my last memories of my sweet sweet lil boy. I love him and don't know why he isn't here today.

"I hope nobody ever has to feel this kind of hurt. I love you Justice. YOU ARE MY SUNSHINE. You stay on my heart and I will never ever forget the precious time that you were here with us."

The attorneys are under a court-issued gag order, according to the district attorney's office.

Green, who is being held without bail, is set to appear in court this week when her trial resumes.