President Trump has come under major scrutiny in recent weeks and months over allegations that he attempted to obstruct the FBI investigation into his former national security advisor, Michael Flynn, and the underlying investigation into Russian attempts to tamper with the election. Several high profile US lawyers have been quoted in the press as suggesting that a case for obstruction of justice could be brought against President Trump. In addition, Mr Trump, Vice President Pence and other administration officials have reportedly hired personal, criminal counsel to represent them.

So what is the US offence of "obstruction of justice", and how does it compare to the UK offence of "perverting the course of justice"?

Obstruction of justice

 In US law obstruction of justice generally means acts which are intended to interfere with or thwart official proceedings (including investigations) and the due administration of justice. The offence is set out in a number of federal statutes.

While some of the statutory provisions cover specific scenarios (for example, killing a witness or destroying evidence) the law also includes broad, catch-all prohibitions. For example, 18 U.S. Code 1503 makes it a crime if someone "corruptly", or "by threats or force", or "by any threatening letter or communication" ... "endeavours to influence, intimidate or impede" any official proceedings or "the due administration of justice." There is disagreement between different Federal circuits as to whether the prosecution must prove a "specific intent" to obstruct justice, or simply that the defendant knowingly and intentionally undertook some action from which obstruction of justice was a reasonably foreseeable result. However, the weight of authority requires proof of a "specific intent" to obstruct justice.

The penalty for obstruction of justice, depending on the specific offence, is up to 20 years' imprisonment and/or a fine.

Although it would be constitutionally difficult for a prosecutor to bring criminal proceedings against President Trump while in office, two former US Presidents have famously been accused of obstruction of justice in the context of impeachment proceedings: Richard Nixon in 1974 and Bill Clinton in 2000. Richard Nixon ultimately resigned, and whilst Bill Clinton was impeached by the House of Representatives, he was subsequently acquitted by the Senate. However, it should be recalled that Bill Clinton's approval rating at the time of his impeachment was over 70%. Impeaching a president is as much (or more) about politics as it is about legalities. According to FiveThirtyEight as at 3 July 2017 President Trump's approval rating is a dismal 39.5% and his disapproval rating is 54.4% (see FiveThirtyEight: How Popular Is Donald Trump?).

Perverting the course of justice

In English law perverting the course of justice is a common law offence, and generally also covers acts which were intended to interfere with or thwart the justice system. Examples include threatening witnesses, interfering with jurors, fabricating or disposing of evidence and providing false information to the police or authorities.

Perverting the course of justice carries the maximum penalty of life imprisonment and/or a fine.

Examples of British politicians convicted of perverting the course of justice include Lord Archer, who was found guilty of providing a false alibi, and former cabinet minister Chris Huhne, whose wife accepted speeding points on his behalf.