[1][3] She enrolled as a part-time student in biology at Chelsea Polytechnic and earned a Bachelor of Science degree from the University of London in 1953.

In 1960, having impressed Nickolls with her ability to handle a hostile lawyer, Pereira was given her first case to work on; this meant she was able to give evidence in court but she faced prejudice as a female expert witness.

[1] In 1969, Pereira was promoted to principal scientific officer and, eight years later, she became director of the Home Counties Forensic Science Laboratory in Aldermaston, Berkshire.

There was no sign of forced entry to the property and much suspicion was placed on the victim's husband; however Pereira's analysis of the case led to the identification of Roger Payne as the murderer.

Pereira was involved in this case as she tested and examined more than 200 blood samples from men ages 16–50 in Beenham, but none of them matched the killer.

[3] Pereira attended La Sainte Union Convent in Bexleyheath and Dartford County Grammar School for Girls and had originally aspired to become a doctor.