Prosecutors say students watched her daily walk before striking
Authorities in southeast Iowa formally accused Jeremy Goodale, 16, and Willard Miller, also 16, of first-degree murder and conspiracy to commit murder in the death of Nohema Graber, 66, in November.
Further details about Ms Graber’s last moments were included in a court filing on 23 December – alleging that both students watched her closely before she was ambushed in an attack on or about 2 November.
That included monitoring her daily walk, during which prosecutors say Mr Goodale and Mr Miller ambushed their Spanish teacher and dragged her body into a nearby wood.
The Fairfield High School teacher was reported missing that day and was found hours later in a park in the area, about 95 miles (150 kilometers) southeast of Des Moines.
Her body was covered by a tarp, wheelbarrow and railroad ties and her body had signs of “inflicted trauma to the head”, authorities had earlier said. Mr Miller also told investigators he was at the park on 2 November.
Police were able to arrest Mr Goodale and later Mr Miller after receiving a tip-off about both students discussing the attack on social media, court documents said.
There were also clothing items left behind at the park in Fairfield that connected the death to both students, who appeared in court for a hearing on 23 December, reports suggest.
A judge, Joel Yates, said he reviewed the information and the minutes of testimony and found “they contain evidence which, if unexplained, is sufficient to warrant a conviction by a trial jury.”
While no trial has been set, both individuals are being held on a $1m cash bond in juvenile detention facilities, and both have pleaded not guilty.
The teenagers are due to be tried as adults because if found guilty as juveniles, they could be released within two years at 18-years-old, the prosecutor argued.
“This prosecuting attorney cannot fathom any combination of programming at any Iowa juvenile facility which could appropriately treat or rehabilitate the defendant if adjudicated as a juvenile,” said the prosecutor.
Additional reporting by The Associated Press.