WASHINGTON, April 19 -- US special counsel Robert Mueller's investigation had looked at 10 actions by President Donald Trump for potential obstruction of justice regarding the investigation into Russian interference in the 2016 election - including the firing of James Comey as the FBI director - but it was unable to determine if the US president did or did not commit a chargeable offence."The evidence we obtained about the president's actions and intent presents difficult issues that would need to be resolved if we were making a traditional prosecutorial judgment," said a redacted copy of Mueller's much awaited report that was released first to the US Congress and then to the public on Thursday....