Murder Mystery: When the Witness is a Tree

Could this wounded tree provide clues to what happened to Bonnie Woodward?

In late June of 2010 Bonnie Woodward went missing. An acquaintance, Roger Carroll, was an early suspect for her assumed murder but police found no evidence of any crime, and never found her body.  For nearly eight years she remained missing and the case went cold.  It was only after Roger Carroll admitted to his wife that he had killed Woodward that critical new information came to light.

 A witness claimed Carroll shot Woodward at his rural Jersey County, Illinois, home, burned her remains in a huge brush pile that he stoked for several days, then used a tractor to push all the evidence – or so he thought – into a creek. Carroll was taken into custody in April of 2018 and charged with first-degree murder.

Police combed the alleged scene of the crime and scoured the area where the brush pile was supposedly burned, but after eight years there was little or no physical evidence to be found, and nothing that definitively linked Woodward to Carroll and his property. However, one investigator with a keen eye noticed that the tree immediately adjacent to the alleged burn site had an unusual wound on its trunk and wondered if it could be a result of being in close proximity to the brush fire. Was it possible this tree could be an independent witness of the disposal of Bonnie Woodward’s body?

Alex Wiedenhoeft, FPL botanist

If a tree is going to be a witness, a translator is needed to get its testimony. Enter Alex Wiedenhoeft, Forest Products Laboratory (FPL) Research Botanist and Team Leader in the Center for Wood Anatomy Research (CWAR). Wiedenhoeft can read trees like most of us read books, and he’s FPL’s resident forensic botany expert. Often when wood is evidence in a crime or accident, law enforcement officials send the samples his way.

“Investigator Frank Scoggins noticed the wound on the tree and decided to find someone who could help him see what, if any, story the tree could tell. He talked to botanists at the nearby Missouri Botanical Garden, and following those leads found his way to the Center for Wood Anatomy Research,” Wiedenhoeft said. Scoggins and Wiedenhoeft initially explored using increment cores from the tree to attempt to date the wound without killing the tree, but that wasn’t adequate to resolve the question.

“When I explained to Frank that what I really wanted was several entire discs – we call them cookies – of the trunk of the tree at multiple heights along the wound, I thought I was asking for too much,” said Wiedenhoeft. “Within a few weeks I received three beautiful cookies sampled exactly as I had requested.”

Tree cookie including the unusual wound collected as evidence and sent to FPL’s Center for Wood Anatomy Research

With the cookies on site in the evidence lockup in the CWAR, Wiedenhoeft was able to study the tree segments up close…extremely close. Because he knew the tree was cut down in late June of 2018 and it was alive when felled, he was able to count the annual growth rings of the tree, working inward from the bark in an uninjured part of the tree. The 2018 growth season was underway when the tree was cut down, so the outermost partial growth ring represented 2018.  He counted inward to 2010 – the time of the alleged burning of Bonnie Woodward’s body, and then moved within the 2010 growth ring toward the wound.  He found, quite clearly, that the wound happened within the 2010 growing season.

“To evaluate the wound itself–the wood formed before wounding, and then wound tissue formed as a part of the tree’s healing process– I asked my colleague and forensic wood anatomist Richard Soares to prepare research-quality microscope sections of this critical area,” said Wiedenhoeft.  “Based on my observations of the cookie and the detailed microscopic analysis of Mr. Soares’ slides, I was able to confirm without doubt that the wound took place in the 2010 growing season.”

Transmitted light micrographs. Left: 2010 growth ring in undamaged portion of the tree. Right:  Degraded 2010 growth ring (lower right) and healthy wound-response tissue (upper left) growing to close over the wound.  Each scale bar is 1 millimeter. (Image credit: Richard Soares.) 

Wiedenhoeft provided his results to the investigators in July 2018, and then went back to his normal research work.  It wasn’t until summer of 2019 that prosecution contacted Wiedenhoeft to discuss the possibility of him being an expert witness in the case.  There was still little other physical evidence, and the tree’s “testimony” was seen as essential to corroborate the witness’ story. The trial was held in March of 2020, and Wiedenhoeft was there to tell the tree’s story.

In order to translate the tree’s message for the jury, he demonstrated the wood science and tree biology behind the analysis. Wiedenhoeft used a machine vision tool he and a colleague at FPL developed called the XyloTron to display a magnified view of the growth rings in real time.  Just as he did back in his lab, he showed the jury the polished, magnified surface of the bark, and then moving inward, came to the partial growth ring from 2018.  2017… 2016… to 2010, and then within 2010 to the wound. 

“I was pretty nervous,” said Wiedenhoeft. “I had never been on the stand before, and it was important to me to be clear to the jury what we can learn from the tree, but also to be completely direct about what we cannot know from the same evidence.”  It wasn’t possible, for instance, for Wiedenhoeft to say definitively that the wound was from a fire, nor could he confirm that the event happened on exactly the dates that the fire was alleged to have occurred.

But what the tree and other evidence had to offer was enough for the jury. After a week-long trial, Roger Carroll was found guilty of first-degree murder, and justice finally prevailed for Bonnie Woodward.