A manhunt for a Rexford woman accused of murdering her 3-year-old niece in August and threatening the child’s family members ended with her arrest Monday in Missoula County.

Tina Marie Mergenthaler, 57, is charged in Lincoln County with felony counts of deliberate homicide, witness tampering and evidence tampering. 

An arrest warrant for Mergenthaler was issued Nov. 6 by Lincoln County Justice of the Peace Jay Sheffield. He found probable cause for the case to proceed following the filing of charges by County Attorney Marcia Boris. 

Sheffield ordered Mergenthaler held without bond. 

Investigators from the Lincoln County Sheriff’s Office, Montana State Crime Lab, Flathead County Sheriff’s Office and Montana Department of Justice’s Division of Criminal Investigation cooperated on the case, which spanned three months, along with help from Oregon officials. 

Charging documents describe chronic abuse and neglect, threats to the victim’s brothers, an attempted cleanup of the crime scene and multiple attempts to deceive authorities investigating the case. 

The investigation began at about 12:42 p.m., Aug. 8 when Lincoln County Sheriff's Office deputies responded to a Pinkham Road home in Rexford after a 911 call indicated a girl had fallen from a tree. 

Deputies found Mergenthaler performing chest compressions on the toddler. She was on the sink counter in the bathroom with only her underwear on. When the deputies took over CPR, Mergenthaler allegedly said the girl “must have hit her head or something … she was knocked out and not breathing so I came in, put her here and started breathing for her … you want to take over, my arms are really tired.” 

Investigators noted Merganthaler wore a black T-shirt, light-colored blue jeans and appeared to have wet hair.  

The little girl’s brothers, ages 5 and 12, were in the home at the time. 

On the day the child died, one of the brothers said his sister fell out of an apple tree when deputies asked him what happened. Mergenthaler allegedly interjected, “You told me the next thing you know is she fell.” 

On Aug. 10, detectives with the Sheriff's Office, along with the county coroner, attended the victim’s exam in Missoula. The medical examiner was confident the girl's injuries were not due to a fall, court documents said. The medical examiner also reported seeing a tread imprint on the toddler’s head. He determined the manner of death to be homicide. 

According to the affidavit, Mergenthaler broke off contact beginning Aug. 11. They reported that she abandoned all of her property at the Pinkham Creek area home. No family members or church members had seen her since Aug. 11. 

On Sept. 1, detectives went to the Pinkham Road property at the landowner's request and allegedly saw towels that appeared stained by bleach. Two days later, investigators returned with an evidence collection team from Flathead County. Trace evidence not visible to the naked eye was seen after a chemical was applied that illuminates when in contact with human blood. 

Oct. 16, state and county authorities met with the medical examiner. He reported that the girl suffered extensive brain bleeding, a broken upper jaw, external healing kidney scars that were weeks old and several rib fractures at different stages of healing. 

RECENT DEVELOPMENTS opened the door for charges to be filed.  

On Nov. 2, state agents met with one of the victim's brothers at the Oregon Department of Human Services Child Care Center in Klamath Falls. The 5-year-old child didn’t want to talk about his time in Montana, but asked after the whereabouts of his aunt, Mergenthaler.  

The child also said he told his foster mother what happened. The agents then spoke to the woman and learned the 5-year-old had been in her care since Aug. 11. 

The woman told investigators that after she returned home from a recent trip, the boy asked her if his aunt was going to be arrested, according to court documents. The woman said she wasn’t aware of it. 

A few moments later, the child returned to his foster mother and said, “She really needs to be arrested.” The woman asked why and he allegedly said, “because she killed my sister.” 

Investigators on Nov. 3 received results from the Montana State Crime Lab that opened the door to criminal charges. State agents received a report that indicated a piece of wood trim seized Sept. 3 contained blood, hair and fibers.  

The charging document also said a DNA report from the crime lab was forthcoming.  

WHILE DETAILS of Mergenthaler's arrest by the U.S. Marshals Service were not immediately available, Missoula County Jail Roster records indicated she was booked into the facility at 10:48 a.m. 

Court officials said Mergenthaler is scheduled to make her initial appearance in Missoula County Justice Court at 2:30 p.m., Tuesday. 

A conviction for deliberate homicide is punishable by life, death or a state prison term for a minimum of 10 years or more than life. 

Convictions on each of the tampering charges are punishable by a maximum term of 10 years in state prison as well as fines up to $60,000. 

    Homicide suspect Tina Mergenthaler is shown here in a photo taken a few days prior to Aug. 8, 2026, the day when Lincoln County authorities say a 3-year-old child died at Mergenthaler's hands. (Courtesy Tobacco Valley News)