Author states that he is owner of his photographs but they have been published in various journals I'm editing a volume and I am responsible to obtain permissions for figures and photographs the authors wish to use in their respective chapters.

Now I have an author A who included several of his own photographs within his chapter which is great. My problem is that most of them have been previously published - in several different journals under several different authors (A is always among the authors). The author stated explicitly that these are his photographs but I'm not so sure. Do journals not normally claim figures along with the text and require even the authors to ask for permission to reuse "their" own content?

Does this apply only to figures or also to photographs? I checked the image caption in several of the publications and it never explicitly states "Photograph taken by A".

Do I need to obtain a permission from the copyright holder/owner of the journal? Should I just create a statement along the lines of 'Photo taken by A, previously published in A et al. 2010'? Should I make A sign a document stating that he always retained the copyright and can therefore license it for use in the present chapter? Should I contact our publisher instead of asking this on StackExchange? Probably, but you guys are much faster ;)

Context: The edited volume will be published in the U.S.A. by a STM-signatory.
The responsibility of certifying and negotiating copyright issues is typically the responsibility of specialized staff at a publishing organization, not that of the scientific editor of a work.

The responsibility of an editor here is just to make sure that the authors follow the process the publishing organization asks the editor to have them follow, which typically includes making copyright assertions or providing contact information to the people who will actually ask them to make copyright assertions.

Thus, if you have concerns, you can convey them to your contacts at the publisher to be sure that they are aware of these concerns and can sort them out. If you aren't the legal personnel responsible for sorting out the details, however, you shouldn't be trying to make any arrangements yourself: that is likely to create more problems than it solves.