Prosecutors say they tried to thwart the investigation of the deadly April explosions by throwing away fireworks and other items they found in Tsarnaev's dorm room the day before his capture.
Authorities say they found the fireworks in a New Bedford, Mass. landfill.
If convicted, they face up to 20 years in prison. Family members of both attended the hearing. According to CBS Boston, federal prosecutors said Tuesday that 15-to-20 witnesses may be called during the trial.
Lawyers for Dias Kadyrbayev and Azamat Tazhayakov- both exchange students from the former Soviet republic of Kazakhstan- denied their clients did anything wrong and fully cooperated with the FBI investigation. The two 19 year olds were in the country on a student visa and were taken into custody on charges they had overstayed their visas.
Another acquaintance of the younger Tsarnaev brother arrested around the same time as Kadyrbayev and Tazhayakov was scheduled to appear in US District court in Boston last month, but the hearing for 19 year old Robel Phillipos had been postponed and he remains free on $100,000 bond.
Several weeks after the arrest of Phillipos, Tazhayakov and Kadyrbayev, FBI agents were interviewing a friend of Tamerlan Tsarnaev in his Orlando, FL-area condo when he allegedly became combative and was shot and killed after attacking one of the agents. Massachusetts State Police believed that Ibragim Todashev and Tamerlan Tsarnaev were suspected of a grisly 2011 triple homicide in Waltham, MA.