Truly wiping an old-style "spinning rust" hard drive takes more than pushing the "delete" button. It involves a process of writing random data to every sector of the hard drive and flipping every bit the opposite way a time or two. This takes a long time. Even then, unless the partition tables are wiped, you can still reconstruct a lot. And even then, the S.M.A.R.T. data is held in an untouchable part of the drive and you can get a lot from that (such as when the drives turned on, when they were active, how much data moved, even their spin speed, temperature, humidity, and lots of other data). A low-level employee in a panic to hide evidence is not going to be a data geek and know all this. If they're the new kind of SSD hard drives, there is no reliable way known yet to wipe them. Restoring data from wiped SSD drives is so easy that the only truly reliable way to wipe them is to shred them.
Truly wiping an old-style "spinning rust" hard drive takes more than pushing the "delete" button. It involves a process of writing random data to every sector of the hard drive and flipping every bit the opposite way a time or two. This takes a long time. Even then, unless the partition tables are wiped, you can still reconstruct a lot. And even then, the S.M.A.R.T. data is held in an untouchable part of the drive and you can get a lot from that (such as when the drives turned on, when they were active, how much data moved, even their spin speed, temperature, humidity, and lots of other data). A low-level employee in a panic to hide evidence is not going to be a data geek and know all this. If they're the new kind of SSD hard drives, there is no reliable way known yet to wipe them. Restoring data from wiped SSD drives is so easy that the only truly reliable way to wipe them is to shred them.