<p>I have an alternative proposal.  Run head detection rather than face detection.  But you would still have to create a dataset for profile faces as I cannot find one yet.  </p>

<p>For face detection, I am currently running DFSD by Tencent on the video on which I want to detect profile faces.  It seems more robust than MTCNN on frontal faces oriented sideways (person lying down).  </p>

<p><a href="https://github.com/TencentYoutuResearch/FaceDetection-DSFD" rel="nofollow noreferrer">Tencent DFSD</a></p>

<p>Head detection has a few Github repos but this one looks really good with models, Arxiv paper and examples:</p>

<p><a href="https://github.com/nyck33/cnn_head_detection" rel="nofollow noreferrer">head detection</a></p>

<p>I'll add a profile face dataset here if I find one. Actually just realized one of the answers above mentions a few such iBug and AFLW, etc.</p>
Dataset and Face Detector for Facial Landmarks of Profile Face
<p>I built a facial landmark predictor for frontal faces (similar to 68 landmarks of dlib). Now, I would like to continue to profile faces. Firstly, what I need is:
1 - A robust detector for profile face.
2 - Profile faces dataset and corresponding landmarks (key-points) annotations.</p>

<p>Any suggestion is welcome. Thanks a lot.</p>