Treason is a very specific crime, the only crime defined in the Constitution.
"Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court. The Congress shall have Power to declare the Punishment of Treason, but no
Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted"
One of the reasons for this is for the protection of those who may be shown to have political issues with the country or its government. Note carefully, that there must be testimony of two witnesses to the same overt act..