Experts asked to establish the age of some former child soldier witnesses in the Lubanga trial admitted on Wednesday that the methods they used were not foolproof.

Despite the admission, the experts told Thomas Lubanga’s attorney Marc Desalliers that the age-determination techniques were the most reliable that are currently in use.

Dr. Caroline Rey-Salmon, a pediatrician and forensic doctor who consults for the French Supreme Court in Paris, testified on Wednesday, along with Catherine Adamsbaum, who also testified the day before and worked with Rey-Salmon.

Rey-Salmon said the x-ray images of the witnesses that she was given by the court to examine were of poor quality and it was not possible to use them to reach a firm conclusion.

“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,” she said.

Rey-Salmon 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,” she said.

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

Both Adamsbaum and Rey-Salmon said examining bones does not always produce the exact age of a person, but experts can come within one year.

In cross-examination by defense attorneys, both experts said that the bone analysis technique was developed during the 1940s in America, based on people of European origin.

They were unaware of any age-determination method based on African populations, and added that poor nutrition, physical exercise, and disease were factors that could lead to unreliable results.