An FBI forensic investigator said Birchmore’s phone contained about 240,000 communications, with roughly 10% involving Farwell. Birchmore sent substantially more messages than Farwell, the investigator testified.

Some messages discussed the pair’s sexual relationship, including an exchange in which Birchmore referred to Farwell taking her virginity. Prosecutors say Farwell began sexually abusing Birchmore when she was a minor. Birchmore was 15 in April 2013, while Farwell was 27. Farwell, a former Stoughton police officer, was required to report suspected abuse of a child, according to the testimony.

Jurors also saw messages describing sexual encounters at a library while Birchmore was in high school. Evidence from her phone showed it was last unlocked and moved during the 9 p.m. hour on the night she died, testimony indicated.

Investigators presented an iCloud note containing a list of baby names, as well as searches made on Farwell’s department-issued phone on the day he turned over his personal phone to Massachusetts State Police. The searches included whether consent can be withdrawn in Massachusetts and whether deleted iMessages can be recovered using Cellebrite, a digital forensics tool used by law enforcement.

Prosecutors allege Farwell killed Birchmore. His guilt has not been established, and the jury will weigh the evidence presented at trial.

FBI special agent Heidi Kelsch testified Friday, and her testimony is expected to resume Monday and continue for multiple days.