 Document analysis in the crime lab emphasizes comparison of materials and writing with known standards  Printing machines (typewriters, printers, etc.) can also be analyzed

 The document in question is compared to a handwriting sample  This sample is the standard and can be either a requested sample or a collected sample  A requested sample is one in which a person is asked to write a dictated text  A collected sample is writing that was done prior to the beginning of the investigation

1. Line quality: do the letters flow or are they written with intent strokes 2. Spacing: what is the average space between words and letters 3. Ratio of height, width, and size of letters: are the letters consistent in height, width and size 4. Lifting pen: does the author lift the pen to stop writing a word and start a new word

5. Connecting strokes: how are capital letters connected to lowercase letters 6. Strokes to begin and end: where does the letter begin and end on a page 7. Unusual letter formation: are any letters written with unusual slants or angles? Are some letters printed rather than written in cursive 8. Pen pressure: how much pressure is applied on upward and downward strokes

9. Slant: do letters slant left or right? A protractor may be used to determine the degree of slant 10. Baseline habits: does the writing go on the line, above the line, or below the line 11. Fancy writing habits: are there any unusual curls or loops or unique styles 12. Placement of diacritics: how are the t’s crossed or the i’s dotted

 Made of a very thin layer of bonded fibers  Usually made of cotton, linen, wood or a combination of these  Some manufacturers place a watermark on their papers; because these change periodically, watermarks can reveal information about the date and origin of a document

 Chromatography works on the basis of absorbance  Two important components of chromatography are the absorbent and the eluent  A good absorbent is a solid material that will attract and absorb the material to be separated  The eluent is the solvent that carries the materials to be separated through the absorbent

 Chromatography works on the principle that compounds to be separated are slightly soluble in the eluent and will spend some of the time in the eluent and some of the time on the absorbent  When the components of a mixture have different solubilities in the eluent, they can be separated from one another  The absorbent is the paper

 The eluent can be any number of solvents including hexanes, cyclohexane, toluene, chloroform, acetone, ethanol, methanol, and water  Choosing the eluent is the most difficult task because the polarity of the eluent determines the level of separation that will be achieved  Inks are mixtures of several basic pigments  Each pigment has a different polarity and can therefore be separated using paper chromatography

 Thymolphthalein is a weak organic acid that behaves as an acid-base indicator in the pH range of 9.3 (HInd colorless) to 10.5 (Ind blue)  By combining thymolphthalein with ethyl alcohol, sodium hydroxide and water at pH 11, a blue disappearing ink is created

 When the blue ink is applied to paper, carbon dioxide mixes with water to form carbonic acid  The acid lowers the pH and the thymolphthalein becomes colorless ◦ CO 2 + H 2 O  H 2 CO 3 ◦ H 2 CO 3 + Ind -  HCO 3 - +HInd