Lying to the Prosecutors

A Massachusetts court just convicted a buddy of the Boston Bomber of "lying to prosecutors".  Pretty wimpy.  This buddy was accused of cleaning up evidence left in Tsarnov's dorm room, including a computer.  Since Tsarnov himself ought to be standing trial for first degree murder, the buddy ought to be charged with accessory to murder, or conspiracy to commit murder. 
  Far as I am concerned, lying to prosecutors should not be a crime.  Prosecutors ought to prosecute on evidence, and testimony, not confessions squeezed out of defendants upon threat of long prison terms. A perp has a right to try and get off by telling the prosecutor/cops  anything he can think of.  If the perp is guilty, the prosecution needs to present real evidence to that effect. 
  Plus, "lying to prosecutors" is something that you can pin on anyone.  Just grill 'em long and hard enough.  Sooner or later the suspect will contradict himself.  Nobody can keep their story straight for ever.  As soon as the suspect makes a slip, charge him with lying.  That's real judicial fairness that is.  Just like they have in Russia.
  And, it's been a long time since we bagged Tsarnov.  When do we bring him to court?  Why are we frying the little fish instead of the big one?   Especially as the little fish were just trying to cover for a buddy.  Which ain't right, but it is understandable.