A federal jury found an Oahu woman guilty Tuesday of assaulting her 15-month-old daughter aboard an Alaska Airlines flight to Honolulu.

Samantha Leialoha Watanabe, 37, faces up to a year in prison at sentencing in March.

The jury, which included 10 women and two men, rejected Watanabe’s claim that her handling of the child while aboard the May 3 flight from Anchorage was lawful parental discipline. The jurors deliberated for half a day before finding Watanabe guilty.

First Assistant Federal Public Defender Alexander Silvert, one of Watanabe’s lawyers, said he plans to file papers seeking to vacate the verdict and dismiss the misdemeanor charge, and, if the court denies the request, will appeal after the court sentences Watanabe.

The state Department of Human Services says privacy laws prevent it from publicly disclosing any information about cases handled by its Child Welfare Services branch. Spokeswoman Keopu Reelitz said, however, that law enforcement officials often report child abuse cases to the CWS even before making an arrest. And she said the state’s response is often faster than the criminal justice system over concern for a child’s safety.

Watanabe has five children older than the girl who was on the flight, and she is now pregnant with her seventh child.

In pretrial hearings Assistant U.S. Attorney Marc Wallenstein said Watanabe had previously gone to trial and had her children removed from her home.

State family court records are confidential. However, a state attorney general child support hearings officer ordered Watanabe in 2008 to pay child support and provide medical insurance for two sons and a daughter, who at the time were 10, 8 and 5 years old, respectively. In 2010 the hearings officer added a 2-1/2-year-old daughter to the order.

Alaska State Trooper Brian Miller; his wife, Cari; and their daughter Rebekah were among 12 family members who were on the same flight as Watanabe. The Mil-lers testified they saw Watanabe pull out her daughter’s hair and hit the child in the front and back of the head with her hand as well as with a Dora the Explorer stuffed doll, causing the toddler’s head to snap fully forward and backward.

The Millers also said Watanabe hit and knocked her daughter off her lap into the next seat, repeatedly picked up and slammed the girl down and repeatedly swore at the child.

“She seemed agitated, nervous, constantly moving in jerky motions with a clenched jaw,” Brian Miller testified.

He told the FBI that based on his 30 years experience as a law enforcement officer, he believed Watanabe was under the influence of a stimulant.

Two flight attendants testified they saw Watanabe lift her daughter off the ground by grabbing the girl’s arm and pulling straight up during boarding in Anchorage.

Arthur Moeller said he told Watanabe to be careful as she could easily dislocate the toddler’s shoulder. He said Watanabe told him, “I do it all the time, she’s used to it.”

Another flight attendant said she saw Watanabe deliver a loud slap on her daughter’s hand as the plane was taxiing toward the runway for takeoff.

“It was an unusually forceful slap, very hard,” Susan Allen testified.

Watanabe’s other lawyer, Assistant Federal Public Defender Craig Jerome, told the jury in closing arguments Monday that what the Millers and flight attendants described didn’t happen. He said they made up the events because they didn’t like the way Watanabe was parenting her child.

A passenger who sat directly behind Watanabe testified that Watanabe and her daughter were noisy during the flight but that she didn’t see Watanabe abuse her child.

State sheriff deputies who were waiting for Watanabe in Honolulu testified that they didn’t arrest Watanabe because they didn’t see any injuries on the child.