By Jim Melwert

WEST CHESTER, Pa. (CBS) -- The Chester County man charged with third-degree murder has wrapped up his testimony in his own defense.

Edward O'Brien is charged with letting his father waste away in what prosecutors call deplorable conditions in a bedroom in his home.

He says he was only following his father's wishes.

The defendant spent more than eight hours on the stand, the defense trying to show his actions were of a loving son trying to fulfill a promise made to his father that he would never put him in a nursing home or long term care.

But the prosecution, on cross-examination, asked about bed sores the father developed in the last weeks of his life. And about bank statements and money transfers made by O'Brien as his father's power of attorney into joint accounts, transfers, which the prosecution says, appear to be the son acting in his own interests rather than his father's.

But on re-direct, O'Brien was again asked why he didn't put his father in a home, his response, in addition to the promise to his father he also feared, if he put him in a home, his father would die of a broken heart.