After more than four days of deliberation, a D.C. Superior Court jury yesterday awarded $750,000 to a 15-year-old Washington girl who lost 90 percent of the use of her right hand in injuries she suffered in 1976 when she fell through a storm door that was not fitted with safety glass.

The jury of six men and six women also awarded an additional $100,000 to the girl's mother for past and future medical expenses that have resulted from the accident.

The girl Zelda Thomas, now a student at the National Cathedral School for Girls, was chasing her sheepdog, which had run outside the house without its collar, when the accident occurred on Aut. 9, 1976. Robert X. Perry Jr., an attorney who represents both the girl and her mother, Cynthia Thomas, a U.S. Department of State employe, said that the glass in the storm door shattered into long shards, cutting the main artery in the girl's right arm.

Perry said in a telephone interview that he argued that the company which installed the glass three years before the accident -- Clark Manufacturing Co. of Silver Spring -- was negligent when it placed ordinary glass in the door instead of safety glass, which shatters on impact into small, less harmful pieces.

Perry said he contended that although no law in the District at the time required installation of safety glass, the company had to know of the growing awarness in the industry of the benefits of using safety glass. Moreover, Perry said that at the time of the accident, 30 states, including Maryland and Virginia, had adopted criminal penalties for failure to use safety glass in bathroom shower doors and storm and patio doors. John Ridge, an attorney who represented Clark, declined to comment on the jury award.

The verdict, reached after a sic-day trial before Judge Leonard Braman, was returned against the estate of a deceased woman who owned the house when the accident occurred at 4741 Fulton St., NW, Perry said. An attorney for the estate could not be reached for comment.