18 U.S.C. § 201 : US Code - Section 201: Bribery of public officials and witnesses

      (a) For the purpose of this section - 
        (1) the term "public official" means Member of Congress,
      Delegate, or Resident Commissioner, either before or after such
      official has qualified, or an officer or employee or person
      acting for or on behalf of the United States, or any department,
      agency or branch of Government thereof, including the District of
      Columbia, in any official function, under or by authority of any
      such department, agency, or branch of Government, or a juror;
        (2) the term "person who has been selected to be a public
      official" means any person who has been nominated or appointed to
      be a public official, or has been officially informed that such
      person will be so nominated or appointed; and
        (3) the term "official act" means any decision or action on any
      question, matter, cause, suit, proceeding or controversy, which
      may at any time be pending, or which may by law be brought before
      any public official, in such official's official capacity, or in
      such official's place of trust or profit.

      (b) Whoever - 
        (1) directly or indirectly, corruptly gives, offers or promises
      anything of value to any public official or person who has been
      selected to be a public official, or offers or promises any
      public official or any person who has been selected to be a
      public official to give anything of value to any other person or
      entity, with intent - 
          (A) to influence any official act; or
          (B) to influence such public official or person who has been
        selected to be a public official to commit or aid in
        committing, or collude in, or allow, any fraud, or make
        opportunity for the commission of any fraud, on the United
        States; or
          (C) to induce such public official or such person who has
        been selected to be a public official to do or omit to do any
        act in violation of the lawful duty of such official or person;

        (2) being a public official or person selected to be a public
      official, directly or indirectly, corruptly demands, seeks,
      receives, accepts, or agrees to receive or accept anything of
      value personally or for any other person or entity, in return
      for:
          (A) being influenced in the performance of any official act;
          (B) being influenced to commit or aid in committing, or to
        collude in, or allow, any fraud, or make opportunity for the
        commission of any fraud, on the United States; or
          (C) being induced to do or omit to do any act in violation of
        the official duty of such official or person;

        (3) directly or indirectly, corruptly gives, offers, or
      promises anything of value to any person, or offers or promises
      such person to give anything of value to any other person or
      entity, with intent to influence the testimony under oath or
      affirmation of such first-mentioned person as a witness upon a
      trial, hearing, or other proceeding, before any court, any
      committee of either House or both Houses of Congress, or any
      agency, commission, or officer authorized by the laws of the
      United States to hear evidence or take testimony, or with intent
      to influence such person to absent himself therefrom;
        (4) directly or indirectly, corruptly demands, seeks, receives,
      accepts, or agrees to receive or accept anything of value
      personally or for any other person or entity in return for being
      influenced in testimony under oath or affirmation as a witness
      upon any such trial, hearing, or other proceeding, or in return
      for absenting himself therefrom;
        shall be fined under this title or not more than three times
      the monetary equivalent of the thing of value, whichever is
      greater, or imprisoned for not more than fifteen years, or both,
      and may be disqualified from holding any office of honor, trust,
      or profit under the United States.

      (c) Whoever - 
        (1) otherwise than as provided by law for the proper discharge
      of official duty - 
          (A) directly or indirectly gives, offers, or promises
        anything of value to any public official, former public
        official, or person selected to be a public official, for or
        because of any official act performed or to be performed by
        such public official, former public official, or person
        selected to be a public official; or
          (B) being a public official, former public official, or
        person selected to be a public official, otherwise than as
        provided by law for the proper discharge of official duty,
        directly or indirectly demands, seeks, receives, accepts, or
        agrees to receive or accept anything of value personally for or
        because of any official act performed or to be performed by
        such official or person;

        (2) directly or indirectly, gives, offers, or promises anything
      of value to any person, for or because of the testimony under
      oath or affirmation given or to be given by such person as a
      witness upon a trial, hearing, or other proceeding, before any
      court, any committee of either House or both Houses of Congress,
      or any agency, commission, or officer authorized by the laws of
      the United States to hear evidence or take testimony, or for or
      because of such person's absence therefrom;
        (3) directly or indirectly, demands, seeks, receives, accepts,
      or agrees to receive or accept anything of value personally for
      or because of the testimony under oath or affirmation given or to
      be given by such person as a witness upon any such trial,
      hearing, or other proceeding, or for or because of such person's
      absence therefrom;
        shall be fined under this title or imprisoned for not more than
      two years, or both.

      (d) Paragraphs (3) and (4) of subsection (b) and paragraphs (2)
    and (3) of subsection (c) shall not be construed to prohibit the
    payment or receipt of witness fees provided by law, or the payment,
    by the party upon whose behalf a witness is called and receipt by a
    witness, of the reasonable cost of travel and subsistence incurred
    and the reasonable value of time lost in attendance at any such
    trial, hearing, or proceeding, or in the case of expert witnesses,
    a reasonable fee for time spent in the preparation of such opinion,
    and in appearing and testifying.
      (e) The offenses and penalties prescribed in this section are
    separate from and in addition to those prescribed in sections 1503,
    1504, and 1505 of this title.