MEXICO CITY — Time seems to have stopped inside cell number six of Barrientos state prison, where Daniel García has been held for more than 16 years without a verdict.

His distorted perception of time became clear more than a decade ago, when he sent his two daughters a dollhouse as a gift, seemingly unaware that they had grown into adults since 2002, when he was accused of murder and locked up.

Mr. García is caught in the legal trappings of Mexico’s old judicial system, which allowed those accused of crimes ranging from murder to minor offenses to be held indefinitely as their cases dragged on for years.

The Mexican government does not keep track of the average time that suspects like Mr. García are kept in pretrial detention. But the United Nations Working Group on Arbitrary Detention, which reviewed his case, has called his arrest “arbitrary” and described the use of preventive prison in his case as “quite exceptional.”