President Trump's former attorney Michael Cohen pleaded guilty to one charge yesterday, and admitted he lied to congress to protect his clients political messaging. This is on top of the eight other counts Cohen pleaded guilty to back in August, and since then he has also spoken extensively with the special counsel's office.

This latest charge was related to the proposed Trump Tower project in Moscow. That seems to add fuel to the fire in the Russia investigation, but also raises some questions about how a lawyer can end up testifying about his client.

Christine Chung of Albany Law School explains.