brian karl brimager , 37 , entered his plea on friday after he was indicted by a federal grand jury in san diego , in connection with the death of yvonne lee baldelli .
he has been in custody since june 2013 on charges including obstruction of justice and falsifying records related to the investigation .
the 42-year-old woman from laguna niguel , california , was last seen in september 2011 when she arrived in panama with brimager .