Photo: Experts say talk of impeachment is increasing after Mr Trump made some big admissions on social media. (AP: Andrew Harnik) Experts say US President Donald Trump could be heading towards impeachment if obstruction of justice accusations are proven. It follows Mr Trump admitting he knew his former national security adviser Michael Flynn had lied to the FBI. So, how does the impeachment process actually work? Simon Jackman, the head of the US Studies Centre at the University of Sydney, took us through the process. What is impeachment? It's a provision in the US Constitution that allows Congress to remove presidents before their term is up. They do this if enough lawmakers vote the president has committed treason, bribery or other high crimes and misdemeanours. Professor Jackman said it was a somewhat misunderstood term. "Impeachment means the beginning of the process that could lead to the removal of the president, impeachment per se is not removal of the president," Professor Jackman said. "Impeachment is actually a step on the road and it's an action taken by the lower house in the United States, the House of Representatives." Professor Jackman said history showed the House will generally send the matter to the House Judiciary Committee before a vote. "If you're looking for an analogy from the legal world, it's like an indictment, it's like a preliminary hearing," Professor Jackman said. Once they've considered the matter, then what's known as articles of impeachment — similar to a charge sheet — can be prepared. Those articles go back to the House for a vote. If one of them gets a majority vote, then impeachment proceedings begin. Once the House votes on impeachment, are they out? Not yet. The matter goes to trial. "In the case of the trial of a sitting US president, the Chief Justice of the Supreme Court becomes the presiding officer of the Senate as it sits as a Court of Impeachment," Professor Jackman said. "Members of the House of Representatives — who supported the motions to impeach the president — are the prosecutors, and the president can bring in essentially whoever he wants to be his defence team." Professor Jackman said in the case of the