Lee is charged with bribing the former president to help cement control of the South Korean tech giant.
He was the de facto leader of one of Asia's largest conglomerates and has been in jail since February on trial for charges ranging from embezzlement to perjury.
He will face the longest prison term on record for a South Korean conglomerate executive if the court finds him guilty on August 25.
Other charges he faces include wrongfully transferring assets overseas and hiding the proceeds of a crime.
Lee insists that he never asked anyone, including the president, for anything for the company or my personal gain.
He stopped several times during his speech, holding back tears.
"I deeply regret that I have given such disappointment and apologize," he added.
The prosecution has said Samsung's paid up for two funds backed by President Park, and sponsoring the equestrian career of the daughter of a confidante at the center of the scandal, was to get government support for efforts to cement Lee's control of the Samsung empire.
"Even though Lee is the ultimate receiver of the gains (from this bribery case), he has been pushing the blame on others accused," prosecutor Park Young-soo told the court.
Park also sought jail terms for other Samsung executives related to the case, including 10 years for Choi Gee-sung, former head of Samsung's corporate strategy office.
The defence questioned whether the prosecution was relying on public sentiment to secure a prison term for Lee, 49, whose father, the group patriarch Lee Kun-hee, was hospitalised in 2014.
Jay Y. Lee's lawyers argued that his so-called overarching intention of cementing ownership control was "a fictional construct" made up by prosecutors, with moves such as the merger of two Samsung affiliates in 2015 aimed merely at ensuring survival and growth of individual companies.