SANFORD, Fla. -

On Friday afternoon, the George Zimmerman's trial defense called their first witness:  The defendant's mother. 

Gladys Zimmerman said while sitting only a short distance away from Trayvon Martin's mom Sybrina Fulton that she knew her son was screaming for help before she killed the unarmed Miami Gardens teen Feb. 26, 2012.

The former court clerk born and raised in Peru said that there was no doubt in her mind that the person who could be heard screaming for help in a 911 call recording was her son.

When defense attorney Mark O'Mara asked her how she knew that it was George Zimmerman, she said, "because he's my son."

Her daughter, Grace Zimmerman, sat in the audience. The family is of Afro-Peruvian descent.

Here is a link to the letter Gladys Zimmerman released April 11, 2013.