Most of the reputable posters here are against double majoring often citing that it’s a lot of work for very little long term gain.
@Platocrat, You can only be admitted into one major so you would have to add the second major once you arrive at your UC. (UCLA?) Since these two fields are practically on opposite sites of the academic spectrum, I’d say it would be very hard as a first time freshman and near impossible as a transfer student especially if you don’t have the majority of the prerequisites complete.
To start off, you would need to meet most of the prerequisites for both majors prior to transferring to be taken seriously by an academic counselor at your eventual UC. Additionally, with the unit limits in place at the UCs, you have a cap to worry about while finishing all the graduation requirements for both majors.
The philosophy major at UCLA has 52 quarter units of upper division major requirements while chemistry needs 47 plus the associated lower division prerequisites which can be as many as 75 quarter units if not previously completed at CC. Coming in with the maximum of 105 units along with the 52 and 47 respective graduation requirements would place you at 204 and with very minimal leeway in regard to the UCLA unit cap of 216 units. Even at the minimum 90 units required to transfer (with no AP credits), you would be at 189 units already which means missing as little as four of the prerequisite courses would make it impossible to double major without a petition approval from a department head.
If UCLA is anything like Berkeley, petitions for unit cap extensions are rarely approved outside of UCEAP considerations.
Sources:
http://www.philosophy.ucla.edu/major.html
http://www.chemistry.ucla.edu/sites/default/files/undergraduate/Chemistry_Major_2014_2015.pdf
http://www.ugeducation.ucla.edu/counseling/max-units.html
If a good portion of your transferable units come from AP scores, and you have completed most of the chemistry major’s extensive list of prerequisites, then it might worth trying to go for it. Otherwise, I would just take additional classes in chemistry as they fit into your schedule. If your adamant on pursuing the double major, your probably better off going to a CSU where the unit limits are much more lenient and such a double major is more feasible.
@uciruby, There is no Chemistry minor available at UCI but there is a Biological Sciences Minor available.
Be careful though as the prerequisites are fairly extensive and UCI has a stricter (relative to UCLA) cap of 9 quarters regardless of units for transfers. Its also important to note that since UCI uses UC-GPA to rank applicants, you would need to take summer courses at a UC (and do very well) in order to have a real shot at adding a second major if you end up going for a second major instead of minoring.
Sources:
http://catalogue.uci.edu/schoolofbiologicalsciences/#minortext
http://www.changeofmajor.uci.edu/CoM_BioSci.html
http://senate.uci.edu/uci-academic-senate-manual/part-ii-regulations-of-the-irvine-division/chapter-i-section-3-scholarship-regulations/regulation-386-credit-hour-unit-limit-undergraduate/
Do you have a specific occupation within forensics that you are interested in? It might be a good idea to read up on this: http://www.utsa.edu/careercenter/pdfs/Forensic%20Science/career_advice_forensic_science.pdf