The detectives followed the couple for five days and could verify that, both F. and J. « were doing many social life activities…
The detectives followed the couple for five days and could verify that, both F. and J. « were doing many social life activities together »: they went to bars, restaurants, and they even went together to a medical centre. The sentence considered that these activities denoted that the relationship of the couple was not only a friendship, but a love affair.