Elizabeth Holmes will soon face a big decision: whether to testify in her own defense in a bid to escape a criminal-fraud conviction.

The Theranos Inc. founder and CEO has been on trial since September, fighting allegations that she defrauded patients and investors about the capabilities of her blood-testing startup, which promised to change healthcare by using a few drops of blood to test for a range of health conditions. Each of the dozen conspiracy and wire fraud charges carries a maximum sentence of 20 years in prison.