Experts in the trial of accused Congolese leader Thomas Lubanga this week struggled to confirm the ages of child soldiers said to have been part of the Union of Congolese Patriots, UPC.

The specialists in age determination testified at the International Criminal Court (ICC) that based on x-ray images, some may have been as young as 10 or 11 years old at the time they were allegedly UPC fighters.

Others, however, probably were not as young, said the experts, pointing out that the quality and limited nature of the images created a margin of error.

The expert testimony was part of the prosecution’s ongoing efforts to prove that some of the former UPC fighters who have testified at The Hague were under the age of 15 when they were trained and used in combat.

Judge Adrian Fulford said these experts were called to help determine the ages of some of the former child soldiers who have given evidence at the trial.

Lubanga has been charged with conscripting and using child soldiers-defined as combatants under the age of 15-in the ethnic fighting that raged in the Ituri region of the eastern Democratic Republic of Congo in 2002 and 2003.

During cross-examination, however, defense lawyers for Lubanga challenged the methodology used and raised doubts about the validity of the expert conclusions.

Despite that, Dr. Caroline Rey-Salmon and Professor Catherine Adamsbaum-forensic medicine experts to the French Supreme Court in Paris-told defense lawyer Marc Desalliers that the age-determination technique employed was the best available.

Adamsbaum said she had looked at x-ray images of the witnesses-together with two other doctors, including Rey-Salmon-which the prosecution said were taken in late 2007 and January 2008.

In late 2007 and early 2008, the witnesses were 15 or 16 years old, according to the experts, suggesting that these former child soldiers were much younger when they served in Lubanga’s militia in 2002 and early 2003.

The age determination technique involves studying the bones of the left wrist and hand, explained the experts, because the development of these body parts indicates the person’s age.

The method is effective for age determination in males less than 20 years old and females less than 17 years old, they said. Beyond those ages, said the experts, these bones are normally fully developed.

Such examination of bones does not always produce the exact age of a person, said the experts, but the age determination is generally accurate within one year.

“Although it is imperfect, the [technique] is the relevant method for assessing age,” said Rey-Salmon.

The experts, who testified separately, said the bone analysis technique was developed more than 50 years ago in America using people of European origin.

Jean Mulamba, a representative of victims at the trial, questioned the validity of the technique for studying African populations.

The experts said they were unaware of any age-determination method based solely on African populations, but noted that poor nutrition, physical exercise, and disease factors could distort results.

The lack of such information “is a limiting factor,” admitted Rey-Salmon.

Besides bone examination, these experts also assessed dental x-rays of witnesses.

The experts explained that dental assessment was used if a decision could not be reached through the analysis of bone images.

Desalliers noted that the particular teeth used in the dental assessments do not appear in every person, and that the appearance of the teeth could be affected by factors other than age.

“Yes, [a tooth] can be missing, it can be pulled out,” Adamsbaum said. “So it is right to say there’s great variability. It is true to say it is hard to try and determine the age of the witness from teeth only.”

Some of the x-ray images that the court provided to the experts were of poor quality, they said.

“The x-rays were of relatively bad quality, and if I had only used those without bone age determination, I wouldn’t have been able to give the age,” said Rey-Salmon.

She also said she was limited by images of only the witness’ jawbone, “I had only jaw x-rays seen from the side and profiles, which are hard to interpret.”

Rey-Salmon said it was hard to determine the age of a person based solely on their dental images. But when combined with bone examination, a more valid result can be achieved, she said.