Takeaways:

1)A one-star review by itself, if purported to be by a patient, may be considered defamatory if ultimately proven to be written by a non-patient.  
2)Multiple one-star reviews, purportedly written by many patients, may be considered defamatory if ultimately proven to be written by one patient. 
3)Even if a doctor has a prior rotten reputation, it is possible for that bad reputation to be made even worse with new defamatory reviews.